RICOH Rx5C348A, Rx5C348B Technical data

’11.04.13

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4-wire Serial Interface

Rx5C348A/B

 OUTLINE

The Rx5C348A/B are CMOS real-time clock ICs connected to the CPU by four signal lines, CE, SCLK, SI, SO, and configured to perform serial transmission of time and calendar data to the CPU. The periodic interrupt circuit is configured to generate interrupt signals with six selectable interrupts ranging from 0.5 seconds to 1 month. The 2 alarm interrupt circuits generate interrupt signals at preset times. As the oscillation circuit is driven under constant voltage, fluctuation of the oscillator frequency due to supply voltage is small, and the time keeping current is small (TYP. 0.35µA at 3V: Rx5C348A, TYP.0.55µA at 3V: Rx5C348B). The oscillation halt sensing circuit can be used to judge the validity of internal data in such events as power-on; The supply voltage monitoring circuit is configured to record a drop in supply voltage below two selectable supply voltage monitoring threshold settings. The 32.768kHz clock output function (N-channel open drain output) is intended to output sub-clock pulses for the external microcomputer. The 32-kHz clock circuit can be disabled by certain register settings for the Rx5C348A but cannot be disabled by any register settings for the Rx5C348B. The oscillation adjustment circuit is intended to adjust time counts with high precision by correcting deviations in the oscillation frequency of the crystal oscillator. These models come in an ultra-compact SSOP10 (RS5C348A/B), SSOP10G (RV5C348A/B), TSSOP10G (RT5C348B) (Limited)

Package 32-kHz Clock Output

RS5C348A Controllable by command RS5C348B RV5C348A Controllable by command RV5C348B RT5C348B TSSOP10G (Pin Pitch 0.5mm, Height0.85mm,

(Limited)

SSOP10 (Pin Pitch 0.5mm, Height1.25mm,

6.4mm×3.5mm) SSOP10G (Pin Pitch 0.5mm, Height1.2mm,

4.0mm×2.9mm)

Keeping output enabled Keeping output enabled

Keeping output enabled

 FEATURES

Timekeeping supply voltage ranging from 1.45 to 5.5V 



Low power consumption Rx5C348A: 0.35µA TYP (0.8µA MAX)



Rx5C348B: 0.55µA TYP (1.0µA MAX)



Only four signal lines (CE, SCLK, SI, and SO) required for connection to the CPU.



Maximum clock frequency of 2 MHz (with VDD = 5V)



Time counters (counting hours, minutes, and seconds) and calendar counters (counting years, months, days, and weeks) (in BCD format)



Interrupt circuit configured to generate interrupt signals (with interrupts ranging from 0.5 seconds to 1 month) to the CPU and provided with an interrupt flag and an interrupt halt



2 alarm interrupt circuits (Alarm_W for week, hour, and minute alarm settings and Alarm_D for hour and minute alarm settings)



32-kHz clock output circuit (Nch. open drain output)



The Rx5C348A is designed to disable 32-kHz clock output in response to a command from the host computer and the Rx5C348B is designed to keep 32-kHz output enabled.



Oscillation halt sensing circuit which can be used to judge the validity of internal data



Supply voltage monitoring circuit with two supply voltage monitoring threshold settings



Automatic identification of leap years up to the year 2099



Selectable 12-hour and 24-hour mode settings



Built-in oscillation stabilization capacitors (CG and CD)



High precision oscillation adjustment circuit



Ultra-compact SSOP10 (RS5C348A/B), SSOP10G (RV5C348A/B), TSSOP10G (RT5C348B) (Limited)



CMOS process

The products scheduled to be discontinued (be sold to limited customer) : "Limited" These products will be discontinued in the future. You can not select these products newly. We will provide these products to the customer who has been using or has ordered them before. But we recommend changing to other products as soon as possible.

at VDD=3V

Rev.2.01 - 1 -

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Rx5C348A/B

 PIN CONFIGURATION

32KOUT

SCLK

Rx5C348A/B

1 2

3 4

9 8 7

VDD OSCIN OSCOUT CE

/INTRVSS

 BLOCK DIAGRAM

32KOUT

OSCIN

OSCOUT

/INTR

32kHz

OUTPUT

CONTROL

OSC

DETECT

DIVIDER

CORREC

-TION

INTERRUPT CONTROL

DIV

TOP VIEW

COMPARATOR_W

COMPARATOR_D

(SEC,MIN,HOUR,WEEK,DAY,MONTH,YEAR)

ADDRESS DECODER

TIME COUNTER

ADDRESS

SHIFT REGISTER

ALARM_W REGISTER

(MIN,HOUR, WEEK)

ALARM_D REGISTER

(MIN,HOUR)

CONTROL

I/O

VDD

VOLTAGE

DETECT

VSS

SCLK SI

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Rev.2.01 - 2 -

Rx5C348A/B

 PIN DESCRIPTION

Symbol Item Description CE Chip enable

Input

SCLK Serial Clock

Input

SI Serial Input The SI pin is used to input data intended for writing in synchronization with

SO Serial Output The SO pin is used to output data intended for reading in synchronization

/INTR Interrupt

Output

32KOUT 32kHz Clock

Output

OSCIN OSCOUT

VDD VSS

Oscillation Circuit Input / Output Positive/Negative Power Supply Input

The CE pin is used for interfacing with the CPU. Should be held high to allow access to the CPU. Incorporates a pull-down resistor. Should be held low or open when the CPU is powered off. Allows a maximum input voltage of 5.5v regardless of supply voltage. The SCLK pin is used to input clock pulses synchronizing the input and output of data to and from the SI and SO pins. Allows a maximum input voltage of 5.5v regardless of supply voltage.

the SCLK pin. CMOS input. Allows a maximum input voltage of 5.5v regardless of supply voltage.

with the SCLK pin. CMOS output.

The /INTR pin is used to output alarm interrupt (Alarm_W) and alarm interrupt (Alarm_D) and output periodic interrupt signals to the CPU signals. Disabled at power-on from 0V. N-channel open drain output. Allows a maximum pull-up voltage of 5.5v regardless of supply voltage. The 32KOUT pin is used to output 32.768-kHz clock pulses. Enabled at power-on from 0 volts. Nch. open drain output. The Rx5C348A is designed to disable 32-kHz clock output in response to a command from the host computer and the Rx5C348B is designed to keep 32-kHz output enabled. The OSCIN and OSCOUT pins are used to connect the 32.768-kHz crystal oscillator (with all other oscillation circuit components built into the Rx5C348A/B).

The VDD pin is connected to the power supply. The VSS pin is grounded.

Rev.2.01 - 3 -

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Rx5C348A/B

 ABSOLUTE MAXIMUM RATINGS

(VSS=0V)

Symbol Item Pin Name Description Unit

VDD Supply Voltage 2 VDD -0.3 to +6.5 V VI Input Voltage CE, SCLK, SI -0.3 to +6.5 V

Output Voltage 1 SO -0.3 to VDD + 0.3 V VO

Output Voltage 2 /INTR, 32KOUT -0.3 to +6.5 V PD Power Dissipation Topt Operating Temperature -40 to +85 Tstg Storage Temperature -55 to +125

Topt = 25°C

300 mW

°C °C

 RECOMMENDED OPERATING CONDITIONS

(VSS=0V, Topt=-40 to +85°C)

Symbol Item Pin Name Min. Typ. Max. Unit Vaccess Supply Voltage Power supply voltage

for interfacing with CPU

VCLK Time keeping Voltage fXT Oscillation Frequency 32.768 kHz

VPUP Pull-up Voltage /INTR, 32KOUT 5.5 V

1.45 5.50 V

2.0 5.5 V

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Rev.2.01 - 4 -

Rx5C348A/B

 DC ELECTRICAL CHARACTERISTICS

(Unless otherwise specified: VSS=0V, VDD=3.0V, Topt=-40 to +85°C, Crystal oscillator 32768Hz,CL=7pF,R1=30kΩ)

Symbol Item Pin Name Conditions Min. Typ. Max. Unit

VIH “H” Input Voltage 0.8x VIL “L” Input Voltage IOH “H” Output

Current

IOL1 /INTR,

IOL2

IIL Input Leakage RDNCE Pull-down Resistance CE 40 120 400

IOZ1 SO VO=5.5V or VSS IOZ2 IDD

(Rx5C34 8A)

IDD (Rx5C34 8B)

VDETH Supply Voltage VDETL Supply Voltage CG Internal Oscillation

“L” Output Current

Current

Output Off-state Current

Time Keeping Current

Monitoring Voltage “H” Monitoring Voltage “L” Capacitance 1

CE, SCLK, SI VDD=2.0 to 5.5V

VDD

-0.3 0.2x

SO VOH=VDD-0.5V -0.5 mA

VOL=0.4V 32KOUT(Rx5C348A ) SO, 32KOUT(Rx5C348B ) SI, SCLK VI=5.5V or VSS

VDD=5.5V

VDD=5.5V /INTR, 32KOUT VO=5.5V

VDD=5.5V VDD VDD=3V,

CE= OPEN

Output = OPEN

32KOUT=OFF

*1) VDD VDD=3V,

CE= OPEN

Output = OPEN

32KOUT=ON VDD

VDD OSCIN 12

Topt=-30 to +70°C

2.0

0.5

-1.0 1.0

-1 1

0.55 1.00

1.90 2.10 2.30

1.45 1.60 1.80

5.5

VDD

0.35 0.80

µA kΩ

µA

CD Internal Oscillation

Capacitance 2

*1) For time keeping current when outputting 32.768kHz from the 32KOUT pin, see “P.40. Typical Characteristics”.

Rev.2.01 - 5 -

OSCOUT 12

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Rx5C348A/B

 AC ELECTRICAL CHARACTERISTICS

Unless otherwise specified: VSS=0V,Topt=-40 to +85°C Input and Output Conditions: VIH=0.8×VDD,VIL=0.2×VDD,VOH=0.8×VDD,VOL=0.2×VDD,CL=50pF

Symbol Item Condi-

tions

CE Set-up Time 400 200 ns

CES

CE Hold Time 400 200 ns

CEH

tCR CE Recovery Time 62 62 f

SCLK Clock

SCLK

1.0 2.0 M

Frequency

SCLK Clock High

CKH

400 200 ns

Time

SCLK Clock Low

CKL

400 200 ns

Time

SCLK Set-up Time 200 100 ns

CKS

tRD Data Output Delay

300 150 ns

Time

tRZ Data Output Floating

300 150 ns

Time

Data Output Delay

CEZ

300 150 ns Time After Falling of CE

tDS Input Data

200 100 ns Set-up Time

tDH Input Data

200 100 ns Hold Time

CKH

VDD≥2.0V VDD≥4.5V Min. Typ. Max. Min. Typ. Max.

CKL

Unit

µs Hz

CES

CKS

SCLK

tRD

*) For reading/writing timing, see “P.28. Adjustment of Oscillation frequency”.

CEH

tCR

CEZ

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Rev.2.01 - 6 -

2.8

0.2

4.0

0.3

005 +0 1

0.55

0.2

 PACKAGE DIMENSIONS

RS5C348A/B (SSOP10) 

3.5±0.2

10 6

0.2

4.4

6.4±0.2

0° to 10°

0.2

0.5

Rx5C348A/B

0.9MAX

0.2±0.1

0.1

0.5

0.1

1.15

0.1

1.35MAX

0.15

+0.1

-0.

unit: mm

RV5C348A/B (SSOP10G) 

+0.3

2.9

-0.1

0.5

0° to 10°

0.127

0.1

1.1

+0.1

-0.05

0.2±0.1

0.1

0.15

0.1

unit: mm

Rev.2.01 - 7 -

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Rx5C348A/B

005 +0 1

RT5C348B (TSSOP10G) 

2.9±0.2

(Limited)

0° to 10°

2.80±0.2

4.0±0.2

0.55±0.2

0.2±0.1

0.5

0.1

0.15

(0.75)

0.1

+0.1

0.13

-0.05

0.85±0.15

unit: mm

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Rev.2.01 - 8 -

Rx5C348A/B

 GENERAL DESCRIPTION

Interface with CPU  The Rx5C348A/B is connected to the CPU by four signal lines CE (Chip Enable), SCLK (Serial Clock), SI (Serial Input), and SO (Serial Output), through which it reads and writes data from and to the CPU. The CPU can be accessed when the CE pin is held high. Access clock pulses have a maximum frequency of 1 MHz allowing high-speed data transfer to the CPU.



Clock and Calendar Function The Rx5C348A/B reads and writes time data from and to the CPU in units ranging from seconds to the last two digits of the calendar year. The calendar year will automatically be identified as a leap year when its last two digits are a multiple of 4. Consequently, leap years up to the year 2099 can automatically be identified as such.

*) The year 2000 is a leap year while the year 2100 is not a leap year.



Alarm Function The Rx5C348A/B incorporates the alarm interrupt circuit configured to generate interrupt signals to the CPU at preset times. The alarm interrupt circuit allows two types of alarm settings specified by the Alarm_W registers and the Alarm_D registers. The Alarm_W registers allow week, hour, and minute alarm settings including combinations of multiple day-of-week settings such as "Monday, Wednesday, and Friday" and "Saturday and Sunday". The Alarm_D registers allow hour and minute alarm settings. The Alarm_W outputs from /INTR pin, and the Alarm_D outputs also from /INTR pin. Each alarm function can be checked from the CPU by using a polling function.



High-precision Oscillation Adjustment Function The Rx5C348A/B has built-in oscillation stabilization capacitors (CG and CD), which can be connected to an external crystal oscillator to configure an oscillation circuit. To correct deviations in the oscillator frequency of the crystal, the oscillation adjustment circuit is configured to allow correction of a time count gain or loss (up to ±1.5ppm at 25°C) from the CPU. The maximum range is approximately ±189ppm in increments of approximately 3ppm. Such oscillation frequency adjustment in each system has the following advantages:

* Allows timekeeping with much higher precision than conventional RTCs while using a crystal oscillator

with a wide range of precision variations. * Corrects seasonal frequency deviations through seasonal oscillation adjustment. * Allows timekeeping with higher precision particularly with a temperature sensing function out of RTC,

through oscillation adjustment in tune with temperature fluctuations.



Power-on Reset, Oscillation Halt Sensing Function and Supply Voltage Monitoring Function The Rx5C348A/B incorporates an oscillation halt sensing circuit equipped with internal registers configured to record any past oscillation halt. Power on reset function reset the control resisters when the system is powered on from 0V. At the same time, the fact is memorized to the resister as a flag, thereby identifying whether they are powered on from 0V or battery backed-up. The Rx5C348A/B also incorporates a supply voltage monitoring circuit equipped with internal registers configured to record any drop in supply voltage below a certain threshold value. Supply voltage-monitoring threshold settings can be selected between 2.1V and 1.6V through internal register settings. The sampling rate is normally 1s. The oscillation halt sensing circuit and the power-on reset flag are configured to confirm the established invalidation of time data in contrast to the supply voltage monitoring circuit intended to confirm the potential invalidation of time data. Further, the supply voltage monitoring circuit can be applied to battery supply voltage monitoring.



Periodic Interrupt Function The Rx5C348A/B incorporates the periodic interrupt circuit configured to generate periodic interrupt signals aside from interrupt signals generated by the alarm interrupt circuit for output from the /INTR pin. Periodic interrupt signals have five selectable frequency settings of 2 Hz (once per 0.5 seconds), 1 Hz (once per 1 second), 1/60 Hz (once per 1 minute), 1/3600 Hz (once per 1 hour), and monthly (the first day of every month). Further, periodic interrupt signals also have two selectable waveforms, a normal pulse form (with a frequency of 2 Hz or 1 Hz) and special form adapted to interruption from the CPU in the level mode (with second, minute, hour, and month interrupts). The condition of periodic interrupt signals can be monitored with using a polling function.



32kHz Clock Output The Rx5C348A/B incorporates a 32-kHz clock circuit configured to generate clock pulses with the oscillation

Rev.2.01 - 9 -

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Rx5C348A/B

frequency of a 32.768kHz crystal oscillator for output from the 32KOUT pin. The 32-kHz clock output can be disabled by certain register settings but cannot be disabled without manipulation of any two registers with different addresses to prevent disabling in such events as the runaway of the CPU. The pin is N-channel open drain output.

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Rev.2.01 - 10 -

Rx5C348A/B

 Address Mapping

Address Register Name D a t a A3A2A1A0 D7 D6 D5 D4 D3 D2 D1 D0

0 0 0 0 0 Second Counter -

*2) 1 0 0 0 1 Minute Counter - M40 M20 M10 M8 M4 M2 M1 2 0 0 1 0 Hour Counter - - H20

3 0 0 1 1 Day-of-week Counter - - - - - W4 W2 W1 4 0 1 0 0 Day-of-month

Counter

5 0 1 0 1 Month Counter and

Century Bit 6 0 1 1 0 Year Counter Y80 Y40 Y20 Y10 Y8 Y4 Y2 Y1 7 0 1 1 1 Oscillation

Adjustment

(Minute Register) 9 1 0 0 1 Alarm_W

(Hour Register) A 1 0 1 0 Alarm_W

(Day-of-week

(Minute Register) C 1 1 0 0 Alarm_D

(Hour Register) D 1 1 0 1 - - - - - - - E 1 1 1 0 Control Register 1

*3) F 1 1 1 1 Control Register 2

*3)

Notes: * 1) All the data listed above accept both reading and writing. * 2) The data marked with "-" is invalid for writing and reset to 0 for reading. * 3) When the XSTP bit is set to 1 in Control Register 2, all the bits are reset to 0 in Oscillation Adjustment Register, Control Register 1 and Control Register 2 excluding the XSTP bit. * 4) Writing to the Oscillation Adjustment Register requires filling the (0) bit. * 5) These bit names apply to the Rx5C348A. For the Rx5C348B the bit names are SCRATCH2 and

SCRATCH3.

- - D20 D10 D8 D4 D2 D1 /19⋅20

(0) *4)

- WM40 WM20 WM10 WM8 WM4 WM2 WM1

- - WH20

- WW6 WW5 WW4 WW3 WW2 WW1 WW0

- DM40 DM20 DM10 DM8 DM4 DM2 DM1

- - DH20

WALE DALE

VDSL VDET SCRA

S40 S20 S10 S8 S4 S2 S1

H10 H8 H4 H2 H1

P⋅/A

- - MO10 MO8 MO4 MO2 MO1

F6 F5 F4 F3 F2 F1 F0

WH10 WH8 WH4 WH2 WH1

WP⋅/ A

DH10 DH8 DH4 DH2 DH1

DP⋅/A

/12⋅24

TCH1

/CLEN2 *5)

XSTP /CLEN1

TEST CT2 CT1 CT0

CTFG WAFG DAFG

*5)

Rev.2.01 - 11 -

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Rx5C348A/B

 Register Settings

Control Register 1 (ADDRESS Eh) 

D7 D6 D5 D4 D3 D2 D1 D0 WALE DALE

WALE DALE 0 0 0 0 0 0 0 0 Default Settings

*1) Default settings: Default value means read / wr itten values when the XSTP bit is set to “1” due to

VDD power-on from 0v or oscillation stopping *2) This bit name applies to the Rx5C348A only. For the Rx5C348B the bit name is SCRATCH3..

(1) WALE, DALE Alarm_W Enable Bit, Alarm_D Enable Bit

WALE,DALE Description

0 Disabling the alarm interrupt circuit (under the control of the settings 1 Enabling the alarm interrupt circuit (under the control of the settings

(2) /12⋅24 /12-24-hour Mode Selection Bit

/12⋅24

0 Selecting the 12-hour mode with a.m. and p.m. indications. (Default) 1 Selecting the 24-hour mode

Setting the /12⋅24 bit to 0 and 1 specifies the 12-hour mode and the 24-hour mode, respectively .

24-hour mode 12-hour mode 24-hour mode 12-hour mode 00 12 (AM12) 12 32 (PM12) 01 01 (AM 1) 13 21 (PM 1) 02 02 (AM 2) 14 22 (PM 2) 03 03 (AM 3) 15 23 (PM 3) 04 04 (AM 4) 16 24 (PM 4) 05 05 (AM 5) 17 25 (PM 5) 06 06 (AM 6) 18 26 (PM 6) 07 07 (AM 7) 19 27 (PM 7) 08 08 (AM 8) 20 28 (PM 8) 09 09 (AM 9) 21 29 (PM 9) 10 10 (AM10) 22 30 (PM10) 11 11 (AM11) 23 31 (PM11)

Setting the /12⋅24 bit should precede writing time data

(3) /CLEN2 (Rx5C348A) 32kHz Clock Output Bit 2

/CLEN2 Description

/12⋅24 /12⋅24

of the Alarm_W registers and the Alarm_D registers). of the Alarm_W registers and the Alarm_D registers)

Description

/CLEN2 *2) /CLEN2 *2)

TEST CT2 CT1 CT0 (For Writing) TEST CT2 CT1 CT0 (For Reading)

*1)

(Default)

0 Enabling the 32-kHz clock circuit (Default)

1 Disabling the 32-kHz clock circuit Setting the /CLEN2 bit or the /CLEN1 bit (D3 in the control register 2) to 0, specifies generating clock pulses with the oscillation frequency of the 32.768-kHz crystal oscillator for output from the 32KOUT pin. Conversely, setting both the /CLEN1 and /CLEN2 bit to 1 disabling (”H”) such output.

SCRATCH3 (Rx5C348B) Scratch Bit 3

SCRATCH3 Description

0 (Default)

1 For the Rx5C348B, this bit is intended for scratching and accepts the reading and writing of 0 and 1. The SCRATCH3 bit will be set to 0 when the XSTP bit is set to 1 in Control Register 2.

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Rev.2.01 - 12 -

(4) TEST T est Bit

TEST Description

0 Normal operation mode. (Default)

1 Test mode. The TEST bit is used only for testing in the factory and should normally be set to 0.

(5) CT2, CT1, and CT0 Periodic Interrupt Selection Bits

CT2 CT1 CT0

0 0 0 - OFF(H) (Default) 0 0 1 - Fixed at “L” 0 1 0 Pulse Mode

0 1 1 Pulse Mode 1 0 0 Level Mode 1 0 1 Level Mode 1 1 0 Level Mode 1 1 1 Level Mode

* 1) Pulse Mode: 2-Hz and 1-Hz clock pulses are output in synchronization with the increment of the

second counter as illustrated in the timing chart below.

Description Wave form mode

*1) *1) *2) *2) *2) *2)

Rx5C348A/B

Interrupt Cycle and Falling Timing

2Hz (Duty50%) 1Hz (Duty50%) Once per 1 second (Synchronized with

second counter increment) Once per 1 minute (at 00 seconds of every minute) Once per hour (at 00 minutes and 00 seconds of every hour) Once per month (at 00 hours, 00 minutes, and 00 seconds of first day of every month)

In the pulse mode, the increment of the second counter is delayed by approximately 92 µs from the

* 2) Level Mode: Periodic interrupt signals are output with selectable interrupt cycle settings of 1 second, 1

CTFG Bit

/INTR Pin

falling edge of clock pulses. Consequently, time readings immediately after the falling edge of clock pulses may appear to lag behind the time counts of the real-time clocks by approximately 1 second. Rewriting the second counter will reset the other time counters of less than 1 second, driving the /INTR pin low.

minute, 1 hour, and 1 month. The increment of the second counter is synchronized with the falling edge of periodic interrupt signals. For example, periodic interrupt signals with an interrupt cycle setting of 1 second are output in synchronization with the increment of the second counter as illustrated in the timing chart below.

pprox. 92µs

(Increment of second counter)

Rewriting of the second counter

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Rev.2.01 - 13 -

Rx5C348A/B

CTFG Bit

/INTR Pin

*1), *2) When the oscillation adjustment circuit is used, the interrupt cycle will fluctuate once per 20sec. or

60sec. as follows: Pulse Mode: The “L” period of output pulses will increment or decrement by a maximum of ±3.784 ms. For example, 1-Hz clock pulses will have a duty cycle of 50 ±0.3784%. Level Mode: A periodic interrupt cycle of 1 second will increment or decrement by a maximum of ±3.784 ms.

Control Register 2 (Address Fh)  D7 D6 D5 D4 D3 D2 D1 D0 VDSL VDET SCRA

VDSL VDET SCRA 0 0 0 1 0 0 0 0 Default Settings *)

*) Default settings: Default value means read / written values when the XSTP bit is set to “1” due to VDD power-on from 0v or oscillation stopping

(1) VDSL VDD Supply Voltage Monitoring Threshold Selection Bit

VDSL Description 0 Selecting the VDD supply voltage monitoring threshold setting of

1 Selecting the VDD supply voltage monitoring threshold setting of

The VDSL bit is intended to select the VDD supply voltage monitoring threshold settings.

(2) VDET Supply Voltage Monitoring Result Indication Bit

VDET Description 0 Indicating supply voltage above the supply voltage monitoring

1 Indicating supply voltage below the supply voltage monitoring

Once the VDET bit is set to 1, the supply voltage monitoring circuit will be disabled while the VDET bit will hold the setting of 1. The VDET bit accepts only the writing of 0, which restarts the supply voltage monitoring circuit. Conversely, setting the VDET bit to 1 causes no event.

(3) SCRATCH1 Scratch Bit 1

SCRATCH1 Description

0 (Default)

1 This bit is intended for scratching and accepts the reading and writing of 0 and 1. The SCRATCH1 bit will be set to 0 when the XSTP bit is set to 1 in Control Register 2.

(4) XSTP Oscillation Halt Sensing Bit

XSTP Description

0 Sensing a normal condition of oscillation

1 Sensing a halt of oscillation (Default) The XSTP bit is for sensing a halt in the oscillation of the crystal oscillator. Oscillation Halt sensing circuit operates only when CE pin is Low.

* The XSTP bit will be set to 1 once a halt in the oscillation of the crystal oscillator is caused by such events as power-on from 0 volts and a drop in supply voltage. The XSTP bit will hold the setting of 1 even after the

Setting CTFG bit to 0

(Increment of second counter)

TCH1 TCH1

2.1v.

1.6v.

threshold settings. threshold settings.

Setting CTFG bit to 0

(Increment of second counter)

XSTP /CLEN1 CTFG WAFG DAFG (For Writing) XSTP /CLEN1 CTFG WAFG DAFG (For Reading)

(Increment of second counter)

(Default)

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Rev.2.01 - 14 -

Rx5C348A/B

restart of oscillation. As such, the XSTP bit can be applied to judge the validity of clock and calendar data after power-on or a drop in supply voltage. * When the XSTP bit is set to 1, all bits will be reset to 0 in the Oscillation Adjustment Register, Control Register 1, and Control Register 2, stopping the output from /INTR pin and starting the output of 32.768-kHz clock pulses from the 32KOUT pin. * The XSTP bit accepts only the writing of 0, which restarts the oscillation halt sensing circuit. Conversely, setting the XSTP bit to 1 causes no event. * It is recommendable to frequently check the XSTP bit for setting errors or data garbles, which may seriously affect the operation of the Rx5C348A/B.

Rev.2.01 - 15 -

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Rx5C348A/B

(5) /CLEN1 32kHz Clock Output Bit 1 (Rx5C348A)

/CLEN1 Description 0 Enabling the 32-kHz clock circuit (Default)

1 Disabling the 32-kHz clock circuit Setting the /CLEN1 bit or the /CLEN2 bit (D4 in the control register 1) to 0, specifies generating clock pulses with the oscillation frequency of the 32.768-kHz crystal oscillator for output from the 32KOUT pin. Conversely, setting both the /CLEN1 and /CLEN2 bit to 1 disabling (”H”) such output.

SCRATCH2 (Rx5C348B) Scratch Bit 2

SCRATCH2 Description

0 (Default)

1 For the Rx5C348B, this bit is intended for scratching and accepts the reading and writing of 0 and 1. The SCRATCH3 bit will be set to 0 when the XSTP bit is set to 1 in Control Register 2.

(6) CTFG Periodic Interrupt Flag Bit

CTFG Description 0 Periodic interrupt output = “H” (Default)

1 Periodic interrupt output = “L” The CTFG bit is set to 1 when the periodic interrupt signals are output from the /INTR pin (“L”). The CTFG bit accepts only the writing of 0 in the level mode, which disables (“H”) the /INTR pin until it is enabled (“L”) again in the next interrupt cycle. Conversely, setting the CTFG bit to 1 causes no event.

(7) WAFG,DAFG Alarm_W Flag Bit and Alarm_D Flag Bit

WAFG,DAFG Description

0 Indicating a mismatch between current time and preset alarm time (Default)

1 Indicating a match between current time and preset alarm time The WAFG and DAFG bits are valid only when the WALE and DALE have the setting of 1, which is caused approximately 61µs after any match between current time and preset alarm time specified by the Alarm_W registers and the Alarm_D registers. The WAFG (DAFG) bit accepts only the writing of 0. /INTR pin outputs off (“H”) when this bit is set to 0. And /INTR pin outputs “L” again at the next preset alarm time. Conversely, setting the WAFG and DAFG bits to 1 causes no event. The WAFG and DAFG bits will have the reading of 0 when the alarm interrupt circuit is disabled with the WALE and DALE bits set to 0. The settings of the WAFG and DAFG bits are synchronized with the output of the /INTR pin as shown in the timing chart below.

pprox. 61µs

WAFG(DAFG) Bit

/INTR Pin

Writing of 0 to

WAFG(DAFG) bit (Match between current time and preset alarm time)

(Match between current time and preset alarm time)

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Rev.2.01 - 16 -

Writing of 0 to

(Match between current time and preset alarm time)

WAFG(DAFG) bit

Rx5C348A/B

Time Counter (Address 0-2h) 

Second Counter (Address 0h)

D7 D6 D5 D4 D3 D2 D1 D0

- S40 S20 S10 S8 S4 S2 S1 (For Writing) 0 S40 S20 S10 S8 S4 S2 S1 (For Reading) 0

Minute Counter (Address 1h)

D7 D6 D5 D4 D3 D2 D1 D0

- M40 M20 M10 M8 M4 M2 M1 (For Writing) 0 M40 M20 M10 M8 M4 M2 M1 (For Reading) 0

Hour Counter (Address 2h)

D7 D6 D5 D4 D3 D2 D1 D0

- 0 0 0 0

*) Default settings: Default value means read / written values when the XSTP bit is set to “1” due to VDD power-on from 0v or oscillation stopping

* Time digit display (BCD format) as follows: The second digits range from 00 to 59 and are carried to the minute digit in transition from 59 to 00. The minute digits range from 00 to 59 and are carried to the hour digits in transition from 59 to 00. The hour digits range as shown in "P12  Control Register 1 (ADDRESS Eh) (2) /12⋅24: /12-24-hour

* Any writing to the second counter resets divider units of less than 1 second. * Any carry from lower digits with the writing of non-existent time may cause the time counters to

Day-of-week Counter (Address 3h) 

D7 D6 D5 D4 D3 D2 D1 D0

- - - - - W4 W2 W1 (For Writing) 0 0 0 0 0 W4 W2 W1 (For Reading) 0 0 0 0 0

*) Default settings: Default value means read / written values when the XSTP bit is set to “1” due to VDD power-on from 0v or oscillation stopping

* The day-of-week counter is incremented by 1 when the day-of-week digits are carried to the * Day-of-week display (incremented in septimal notation): * Correspondences between days of the week and the day-of-week digits are user-definable

(e.g. Sunday = 0, 0, 0) * The writing of (1, 1, 1) to (W4, W2, W1) is prohibited except when days of the week are unused.

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

P⋅/A

or H20

P⋅/A

or H20

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

Mode Selection Bit" and are carried to the day-of-month and day-of-week digits in transition from PM11 to AM12 or from 23 to 00.

malfunction. Therefore, such incorrect writing should be replaced with the writing of existent time data.

day-of-month digits. (W4, W2, W1) = (0, 0, 0) → (0, 0, 1)→…→(1, 1, 0) → (0, 0, 0)

H10 H8 H4 H2 H1 (For Writing) H10 H8 H4 H2 H1 (For Reading)

Indefinite Indefinite Indefinite

Default Settings *)

Rev.2.01 - 17 -

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Rx5C348A/B

Calendar Counter (Address 4-6h) 

Day-of-month Counter (Address 4h)

D7 D6 D5 D4 D3 D2 D1 D0

- - D20 D10 D8 D4 D2 D1 (For Writing) 0 0 D20 D10 D8 D4 D2 D1 (For Reading) 0 0

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

Month Counter + Century Bit (Address 5h)

D7 D6 D5 D4 D3 D2 D1 D0 /19⋅20 /19⋅20

Indefinite

- - MO10 MO8 MO4 MO2 MO1 (For Writing) 0 0 MO10 MO8 MO4 MO2 MO1 (For Reading) 0 0

Indefinite Indefinite Indefinite Indefinite Indefinite

Year Counter (Address 6h)

D7 D6 D5 D4 D3 D2 D1 D0 Y80 Y40 Y20 Y10 Y8 Y4 Y2 Y1 (For Writing) Y80 Y40 Y20 Y10 Y8 Y4 Y2 Y1 (For Reading)

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

*) Default settings: Default value means read / written values when the XSTP bit is set to “1” due to VDD power-on from 0v or oscillation stopping

* The calendar counters are configured to display the calendar digits in BCD format by using the

automatic calendar function as follows:

The day-of-month digits (D20 to D1) range from 1 to 31 for January, March, May, July, August,

October, and December; from 1 to 30 for April, June, September, and November; from 1 to 29 for February in leap years; from 1 to 28 for February in ordinary years. The day-of-month digits are carried to the month digits in reversion from the last day of the month to 1. The month digits (MO10 to MO1) range from 1 to 12 and are carried to the year digits in reversion from 12 to 1.

The year digits (Y80 to Y1) range from 00 to 99 (00, 04, 08, …, 92, and 96 in leap years) and are

carried to the /19⋅20 digits in reversion from 99 to 00. The /19⋅20 digits cycle between 0 and 1 in reversion from 99 to 00 in the year digits. * Any carry from lower digits with the writing of non-existent calendar data may cause the calendar

counters to malfunction. Therefore, such incorrect writing should be replaced with the writing of

existent calendar data.

Oscillation Adjustment Register (Address 7h) 

D7 D6 D5 D4 D3 D2 D1 D0 (0) F6 F5 F4 F3 F2 F1 F0 (For Writing) (0) F6 F5 F4 F3 F2 F1 F0 (For Reading) 0 0 0 0 0 0 0 0 Default Settings *)

*) Default settings: Default value means read / written values when the XSTP bit is set to “1” due to VDD power-on from 0v or oscillation stopping

(0) bit The (0) bit should be set to 0 to allow writing to the Oscillation Adjustment Register. The (0) bit will be set to 0 when the XSTP bit is set to 1 in the Control Register 2.

F6 to F0 bits The Oscillation Adjustment Circuit is configured to change time counts of 1 second on the basis of the settings of the Oscillation Adjustment Register when the second digits read 00, 20, or 40 seconds. Normally, the Second Counter is incremented onc e per 32768 32.768-kHz clock pulses generated by the crystal oscillator. Writing to the F6 to F0 bits activates the oscillation adjustment circuit.

* The Oscillation Adjustment Circuit will not operate with the same timing (00, 20, or 40 seconds) as the timing of writing to the Oscillation Adjustment Register. * The F6 bit setting of 0 causes an increment of time counts by ((F5, F4, F3, F2, F1, F0) - 1) x 2. The F6 bit setting of 1 causes a decrement of time counts by ((/F5, /F4, /F3, /F2, /F1, /F0) + 1) x 2. The settings of "*, 0, 0, 0, 0, 0, *" ("*" representing either "0" or "1") in the F6, F5, F4, F3, F2, F1, and F0 bits

Default Settings *)

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Rev.2.01 - 18 -

Rx5C348A/B

cause neither an increment nor decrement of time counts. Example:

When the second digits read 00, 20, or 40, the settings of "0, 0, 0, 0, 1, 1, 1" in the F6, F5, F4, F3, F2, F1, and F0 bits cause an increment of the current time counts of 32768 by (7 - 1) x 2 to 32780 (a current time count loss). When the second digits read 00, 20, or 40, the settings of "0, 0, 0, 0, 0, 0, 1" in the F6, F5, F4, F3, F2, F1, and F0 bits cause neither an increment nor a decrement of the current time counts of 32768. When the second digits read 00, 20, or 40, the settings of "1, 1, 1, 1, 1, 1, 0" in the F6, F5, F4, F3, F2, F1, and F0 bits cause a decrement of the current time counts of 32768 by (- 2) x 2 to 32764 (a current time count gain).

An increase of two clock pulses once per 20 seconds causes a time count loss of approximately 3 ppm (2 / (32768 x 20 = 3.051 ppm). Conversely, a decrease of two clock pulses once per 20 seconds causes a time count gain of 3 ppm. Consequently, deviations in time counts can be corrected with a precision of ±1.5 ppm. Note that the oscillation adjustment circuit is configured to correct deviations in time counts and not the oscillation frequency of the 32.768-kHz clock pulses. For further details, see "P.30 Oscillation Adjustment Circuit".

Alarm_W Registers (Address 8-Ah) 

Alarm_W Minute Register (Address 8h)

D7 D6 D5 D4 D3 D2 D1 D0

- WM40 WM20 WM10 WM8 WM4 WM2 WM1 (For Writing) 0 WM40 WM20 WM10 WM8 WM4 WM2 WM1 (For Reading) 0

Alarm_W Hour Register (Address 9h)

D7 D6 D5 D4 D3 D2 D1 D0

- - WH20 0 0 WH20 0 0

Alarm_W Day-of-week Register (Address Ah)

D7 D6 D5 D4 D3 D2 D1 D0

- WW6 WW5 WW4 WW3 WW2 WW1 WW0 (For Writing) 0 WW6 WW5 WW4 WW3 WW2 WW1 WW0 (For Reading) 0

*) Default settings: Default value means read / written values when the XSTP bit is set to “1” due to VDD power-on from 0v or oscillation stopping

* The D5 bit of the Alarm_W Hour Register represents WP/A when the 12-hour mode is selected (0 for * The Alarm_W Registers should not have any non-existent alarm time settings.

(Note that any mismatch between current time and preset alarm time specified by the Alarm_W registers * When the 12-hour mode is selected, the hour digits read 12 and 32 for 0 a.m. and 0 p.m., respectively. * WW0 to WW6 correspond to W4, W2, and W1 of the day-of-week counter with settings ranging from * WW0 to WW6 with respective settings of 0 disable the outputs of the Alarm_W Registers.

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

WH10 WH8 WH4 WH2 WH1 (For Writing)

WP⋅/A

WH10 WH8 WH4 WH2 WH1 (For Reading)

WP⋅/A

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

a.m. and 1 for p.m.) and WH20 when the 24-hour mode is selected (tens in the hour digits).

may disable the alarm interrupt circuit.)

(See "P12 Control Register 1 (ADDRESS Eh) (2) /12⋅24: 12-/24-hour Mode Selection Bit")

(0, 0, 0) to (1, 1, 0).

Default Settings *)

Rev.2.01 - 19 -

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Rx5C348A/B

Example of Alarm Time Setting

Alarm Day-of-week 12-hour mode 24-hour mode Preset alarm time Sun. Mon. Tue. Wed. Th. Fri. Sat. 10

hr. 1 hr.

10 min. 1 min.

10 hr. 1 hr.

10 min.1 min.

00:00 a.m. on all days 1 1 1 1 1 1 1 1 2 0 0 0 0 0 0 01:30 a.m. on all days 1 1 1 1 1 1 1 0 1 3 0 0 1 3 0 11:59 a.m. on all days 1 1 1 1 1 1 1 1 1 5 9 1 1 5 9 00:00 p.m. on Mon. to Fri. 0 1 1 1 1 1 0 3 2 0 0 1 2 0 0 01:30 p.m. on Sun. 1 0 0 0 0 0 0 2 1 3 0 1 3 3 0 11:59 p.m. on Mon. ,Wed., and Fri.

WW0 WW1 WW2 WW3 WW4 WW5 WW6

0 1 0 1 0 1 0 3 1 5 9 2 3 5 9

Note that the correspondence between WW0 to WW6 and the days of the week shown in the above table is only an example and not mandatory.

Alarm_D Register (Address B-Ch) 

Alarm_D Minute Register (Address Bh)

D7 D6 D5 D4 D3 D2 D1 D0

- DM40 DM20 DM10 DM8 DM4 DM2 DM1 (For Writing) 0 DM40 DM20 DM10 DM8 DM4 DM2 DM1 (For Reading) 0

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

Default Settings *)

Alarm_D Hour Register (Address Ch)

D7 D6 D5 D4 D3 D2 D1 D0

- - DH20

DH10 DH8 DH4 DH2 DH1 (For Writing)

DP⋅/A

0 0 DH20

DH10 DH8 DH4 DH2 DH1 (For Reading)

DP⋅/A

0 0

Indefinite Indefinite Indefinite Indefinite Indefinite Indefinite

Default Settings *) *) Default settings: Default value means read / written values when the XSTP bit is set to “1” due to VDD power-on from 0v or oscillation stopping

* The D5 bit represents DP/A when the 12-hour mode is selected (0 for a.m. and 1 for p.m.) and DH20

when the 24-hour mode is selected (tens in the hour digits). * The Alarm_D registers should not have any non-existent alarm time settings. (Note that any mismatch between current time and preset alarm time specified by the Alarm_D registers

may disable the alarm interrupt circuit.) * When the 12-hour mode is selected, the hour digits read 12 and 32 for 0a.m. and 0p.m., respectively. (See "P12 Control Register 1 (ADDRESS Eh) (2) /12⋅24: 12-/24-hour Mode Selection Bit")

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Rx5C348A/B

 Interfacing with the CPU

DA TA TRANSFER FORMATS  (1) Timing Between CE Pin Transition and Data Input / Output The Rx5C348A/B adopts a 4-wire serial interface by which they use the CE (Chip Enable), SCLK (Serial Clock), SI (Serial Input), and SO (Serial Output) pins to receive and send data to and from the CPU. The 4-wire serial interface provides two types of input/output timings with which the SO pin output and the SI pin input are synchronized with the rising or falling edges of the SCLK pin input, respectively, and vice versa. The Rx5C348A/B is configured to select either one of two different input/output timings depending on the level of the SCLK pin in the low to high transition of the CE pin. Namely, when the SCLK pin is held low in the low to high transition of the CE pin, the models will select the timing with which the SO pin output is synchronized with the rising edge of the SCLK pin input, and the SI pin input is synchronized with the falling edge of the SCLK pin input, as illustrated in the timing chart below.

Conversely, when the SCLK pin is held high in the low to high transition of the CE pin, the models will select the timing with which the SO pin output is synchronized with the falling edge of the SCLK pin input, and the SI pin input is synchronized with the rising edge of the SCLK pin input, as illustrated in the timing chart below.

SCLK

CES

tDS

tDH

SCLK

tDH

(2) Data Transfer Formats Data transfer is commenced in the low to high transition of the CE pin input and completed in its high to low transition. Data transfer is conducted serially in multiple units of 1 byte (8 bits). The former 4 bits are used to specify in the Address Pointer a head address with which data transfer is to be commenced from the host. The latter 4 bits are used to select either reading data transfer or writing data transfer, and to set the Transfer Format Register to specify an appropriate data transfer format. All data transfer formats are designed to transfer the most significant bit (MSB) first.

SCL

the Address Pointe

A1 A0 C3 C2 C1 C0

Setting

75823123 1 4

Setting the Transfer

Format Register

D7 D6 D3 D2 D1 D0

Writing data transfer

D7 D6 D3 D2 D1 D0

Reading data transfer

Two types of dat a transfer formats are available for reading data transfer and writing data transfer each.

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Rev.2.01 - 21 -

Rx5C348A/B

Writing Data Transfer Formats  (1) 1-byte Writing Data Transfer Format The first type of writing data transfer format is designed to transfer 1-byte data at a time and can be selected by specifying in the address pointer a head address with which writing data transfer is to be commenced and then writing the setting of 8h to the transfer format register. This 1-byte writing data transfer can be completed by driving the CE pin low or continued by specifying a new head address in the address pointer and setting the data transfer format.

Example of 1-byte Wr i t ing Data Transfer (For Wri t ing Data to Addresses Fh and 7h)

1 1

01 0 01 1

Data Data

0 11 0 0 01 1

Specifying Fh in the

ddress

Pointer

Setting 8h in the Transfer Format

Data transfer from the host

Writing data to address Fh

Specifying 7h in the

ddress

Pointer

Setting 8h in the Transfer Format

Writing data to address 7h

Data transfer from the RTCs

(2) Burst Writing Data Transfer Format The second type of writing data transfer format is designed to transfer a sequence of data serially and can be selected by specifying in the address pointer a head address with which writing data transfer is to be commenced and then writing the setting of 0h to the transfer format register. The address pointer is incremented for each transfer of 1-byte data and cycled from Fh to 0h. This burst writing data transfer can be completed by driving the CE pin low.

Example of Burst Writing Data T r ansfer (For Writing Dat a t o Addr esses Eh, Fh, and 0h)

1 0

00 0 01 1

Data

Specifying Eh in the

ddress

Pointer

Setting 0h in the Transfer Format

Writing data to address Eh

Writing data to address Fh

Data transfer from the host Data transfer from the RTCs

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Rev.2.01 - 22 -

Writing data to address 0h

Rx5C348A/B

Reading Data Transfer Formats  (1) 1-byte Reading Data Transfer Format The first type of reading data transfer format is designed to transfer 1-byte data at a time and can be selected by specifying in the Address Pointer a head address with which reading data transfer is to be commenced and then the setting of writing Ch to the Transfer Format Register. This 1-byte reading data transfer can be completed by driving the CE pin low or continued by specifying a new head address in the Address Pointer and selecting this type of reading data T ransfer Format.

Example of 1-byte Reading Data Transfer (For Readi ng Dat a f r om Addr esses Eh and 2h)

1 0

Specifying Eh in the

ddress

Pointer

11 0 01 1 0 10 1 0 00 1

Data Data

Setting Ch in the Transfer Format

Reading data from address Eh

Data transfer from the host Data transfer from the RTCs

Specifying 2h in the

ddress

Pointer

Setting Ch in the Transfer Format

Reading data from address 2h

(2) Burst Reading Data Transfer Format The second type of reading data transfer format is designed to transfer a sequence of data serially and can be selected by specifying in the address pointer a head address with which reading data transfer is to be commenced and then writing the setting of 4h to the transfer format register. The address pointer is incremented for each transfer of 1-byte data and cycled from Fh to 0h. This burst reading data transfer can be completed by driving the CE pin low.

Example of Burst Reading Data Transfer (For Reading Data from Addr esses Fh, 0h, and 1h)

1 1

10 0 01 1

Specifying Fh in the

ddress

Pointer

Setting 4h in the Transfer Format

Data transfer from the host Data transfer from the RTCs

DATA

Reading data from address Fh

DATA

Reading data from address 0h

Rev.2.01 - 23 -

DATA

Reading data from address 1h

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Rx5C348A/B

(3) Combination of 1-byte Reading and writing Data Transfer Formats The 1-byte reading and writing data transfer formats can be combined together and further followed by any other data transfer format.

Example of Reading Modify Writing Data T r ansfer

(For Reading and Writing Data f r om and to Address Fh)

DATASI

Writing data to address Fh

1 1

Specifying Fh in the

ddress

Pointer

11 0 01 1 1 11 0 0 01 1

DATA

Setting Ch in the Transfer Format

Reading data from address Fh

Data transfer from the host Data transfer from the RTCs

Specifying Fh in the

ddress

Pointer

Setting 8h in the Transfer Format

The reading and writing data transfer formats correspond to the settings in the transfer format register as shown in the table below.

1 Byte Burst Writing data transfer Reading data transfer

8h (1,0,0,0) Ch (1,1,0,0)

0h (0,0,0,0) 4h (0,1,0,0)

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Rx5C348A/B

Considerations in Reading and Writing Time Data under special condition  Any carry to the second digits in the process of reading or writing time data may cause reading or writing erroneous time data. For example, suppose a carry out of 13:59:59 into 14:00:00 occurs in the process of reading time data in the middle of shifting from the minute digits to the hour digits. At this moment, the second digits, the minute digits, and the hour digits read 59 seconds, 59 minutes, and 14 hours, respectively (indicating 14:59:59) to cause the reading of time data deviating from actual time virtually 1 hour. A similar error also occurs in writing time data. To prevent such errors in reading and writing time data, the Rx5C348A/B has the function of temporarily locking any carry to the second digits during the high interval of the CE pin and unlocking such a carry in its high to low transition. Note that a carry to the second digits can be locked for only 1 second, during which time the CE pin should be driven low.

Actual time

Time counts within RTC

The effective use of this function requires the following considerations in reading and writing time data: (1) Hold the CE pin high in each session of reading or writing time data. (2) Ensure that the high interval of the CE pin lasts within 1 second. Should there be any possibility of the host going down in the process of reading or writing time data, make arrangements in the peripheral circuitry as to drive the CE pin low or open at the moment that the host actually goes down. (3) Leave a time span of 31µs or more from the low to high transition of the CE pin to the start of access to addresses 0h to 6h in order that any ongoing carry of the time digits may be completed within this time span. (4) Leave a time span of 62µs or more from the high to low transition of the CE pin to its low to high transition in order that any ongoing carry of the time digits during the high interval of the CE pin may be adjusted within this time span.

The considerations listed in (1), (3), and (4) above are not required when the process of reading or writing time data is obviously free from any carry of the time digits. (e.g. reading or writing time data in synchronization with the periodic interrupt function in the level mode or the alarm interrupt function).

Good and bad examples of reading and writing time data are illustrated on the next page.

13:59:59 14:00:00 14:00:01

Max.62µs

13:59:59

14:00:00

14:00:01

Rev.2.01 - 25 -

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Rx5C348A/B

Good Example

Time span of 31µs or more

ny address other than addresses 0h to 6h permits of immediate reading or writing without requiring a time span of 31 µs.

SI SO

F4h

ddress Pointer = Fh Transfer Format Register = 4h

DATA

Reading from

ddress Fh

(control2)

DATA

Reading from

ddress 0h

(sec.)

DATA

Reading from

ddress 1h

(min.)

DATA

Reading from

ddress 2h

(hr.)

Bad Example (1) (Where the CE pin is once driven low in the process of reading time data)

31µs or more

CE SI

0Ch

ddress Pointer = 0h Transfer Format Register = Ch

Data

Reading from

ddress 0h

(sec.)

14h

ddress Pointer = 1h Transfer Format Register = 4h

Data

Reading from

ddress 1h

(min.)

Data

Reading from

ddress 2h

(hr.)

Bad Example (2) (Where a time span of less than 31µs is left until the start of the process of writing time data)

Time span of less than 31µs

F0h

Data Data Data Data

Writing to

ddress 0h

(sec.)

Writing to

ddress 1h

(min.)

Writing to

ddress 2h

(hr.)

= Fh Transfer Format Register = 0h

Bad Example (3)

ddress Pointer

Writing to

ddress Fh

(contorl2)

(Where a time span of less than 61µs is left between the adjacent processes of reading time data)

Less than 62µs

SI SO

0Ch

Data

ddress Pointer = 0h Transfer Format Register = Ch

Reading from

ddress 0h

(sec.)

Data transfer from the host

Data

0Ch

Data

ddress Pointer = 0h Transfer Format Register = Ch

Reading from

(sec.)

ddress 0h

Data transfer from RTCs

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Rev.2.01 - 26 -

Rx5C348A/B

 Configuration of Oscillation Circuit and Correction of Time Count Deviations

Configuration of Oscillation Circuit 

VDD

OSCIN

The oscillation circuit is driven at a constant voltage of approximately 1.2v relative to the level of the VSS pin input. As such, it is configured to generate an oscillating waveform with a peak-to-peak voltage on the order of

1.2v on the positive side of the VSS pin input. < Considerations in Handling Crystal Oscillators >

Generally, crystal oscillators have basic characteristics including an equivalent series resistance (R1) indicating the ease of their oscillation and a load capacitance (CL) indicating the degree of their center frequency. Particularly, crystal oscillators intended for use in the Rx5C348A/B are recommended to have a typical R1 value of 30kΩ and a typical CL value of 6 to 8pF. To confirm these recommended values, contact the manufacturers of crystal oscillators intended for use in these particular models.

< Considerations in Installing Components around the Oscillation Circuit >

1) Install the crystal oscillator in the closest possible vicinity to the real-time clock ICs.

2) Avoid laying any signal lines or power lines in the vicinity of the oscillation circuit (particularly in the area marked "A" in the above figure).

3) Apply the highest possible insulation resistance between the OSCIN and OSCOUT pins and the printed circuit board.

4) Avoid using any long parallel lines to wire the OSCIN and OSCOUT pins.

5) Take extreme care not to cause condensation, which leads to various problems such as oscillation halt. < Other Relevant Considerations >

1) For external input of 32.768-kHz clock pulses to the OSCIN pin: DC coupling: Prohibited due to an input level mismatch. AC coupling: Permissible except that the oscillation halt sensing circuit does not guarantee perfect operation because it may cause sensing errors due to such factors as noise.

2) To maintain stable characteristics of the crystal oscillator, avoid driving any other IC through 32.768-kHz clock pulses output from the OSCOUT pin.

CG RD

32kHz

OSCOUT

VDD

Typical externally-equipped element X’tal : 32.768kHz (R1=30kΩ typ) (CL=6pF to 8pF) Standard values of internal elements RF 15MΩ RD 120kΩ typ CG,CD 12pF typ

typ

Rev.2.01 - 27 -

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Rx5C348A/B

Measurement of Oscillation Frequency 

OSCOUT

32KOUT

VDD

OSCIN

VSS

32768Hz

Frequency

Counter

* 1) The Rx5C348A/B is configured to generate 32.768-kHz clock pulses for output from the 32KOUT pin. * 2) A frequency counter with 6 (more preferably 7) or more digits on the order of 1ppm is recommended

for use in the measurement of the oscillation frequency of the oscillation circuit.

Adjustment of Oscillation frequency  The oscillation frequency of the oscillation circuit can be adjusted by varying procedures depending on the usage of Model Rx5C348A/B in the system into which they are to be built and on the allowable degree of time count errors. The flow chart below serves as a guide to selecting an optimum oscillation frequency adjustment procedure for the relevant system.

Start

Use 32-kHz

clock output?

YES

Use 32-kHz clock output without regard

to its frequency precision

llowable time count precision on order of oscillation frequency variations of crystal oscillator (*1) plus frequency variations of RTC (*2)? (*3)

llowable time count precision on order of oscillation

frequency variations of crystal oscillator (*1) plus frequency variations of RTC (*2)? (*3)

YES

Course (A)

Course (B)

Course (C)

Course (D)

* 1) Generally, crystal oscillators for commercial use are classified in terms of their center frequency

depending on their load capacitance (CL) and further divided into ranks on the order of ±10, ±20, and ±50ppm depending on the degree of their oscillation frequency variations.

* 2) Basically, Model Rx5C348A/B is configured to cause frequency variations on the order of ±5 to

±10ppm at 25°C.

* 3) Time count precision as referred to in the above flow chart is applicable to normal temperature and

actually affected by the temperature characteristics and other properties of crystal oscillators.

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Rev.2.01 - 28 -

Rx5C348A/B

Course (A) When the time count precision of each RTC is not to be adjusted, the crystal oscillator intended for use in that RTC may have any CL value requiring no presetting. The crystal oscillator may be subject to frequency variations which are selectable within the allowable range of time count precision. Several crystal oscillators and RTCs should be used to find the center frequency of the crystal oscillators by the method described in "P.28  Adjustment of Oscillation frequency" and then calculate an appropriate oscillation adjustment value by the method described in "P.30  Oscillation Adjustment Circuit" for writing this value to the Rx5C348A/B.

Course (B) When the time count precision of each RTC is to be adjusted within the oscillation frequency variations of the crystal oscillator plus the frequency variations of the real-time clock ICs, it becomes necessary to correct deviations in the time count of each RTC by the method described in " P.30  Oscillation Adjustment Circuit". Such oscillation adjustment provides crystal oscillators with a wider range of allowable settings of their oscillation frequency variations and their CL values. The real-time clock IC and the crystal oscillator intended for use in that real-time clock IC should be used to find the center frequency of the crystal oscillator by the method described in " P28  Measurement of Oscillation Frequency " and then confirm the center frequency thus found to fall within the range adjustable by the oscillation adjustment circuit before adjusting the oscillation frequency of the oscillation circuit. At normal temperatur e, the oscillation frequency of the oscillator circuit can be adjusted by up to approximately ±0.5ppm.

Course (C) Course (C) together with Course (D) requires adjusting the time count precision of each RTC as well as the frequency of 32.768-kHz clock pulses output from the 32KOUT pin. Normally, the oscillation frequency of the crystal oscillator intended for use in the RTCs should be adjusted by adjusting the oscillation stabilizing capacitors CG and CD connected to both ends of the crystal oscillator. The Rx5C348A/B, which incorporate the CG and the CD, require adjusting the oscillation frequency of the crystal oscillator through its CL value. Generally, the relationship between the CL value and the CG and CD values can be represented by the following equation: CL = (CG × CD)/(CG + CD) + CS where "CS" represents the floating capacity of the printed circuit board. The crystal oscillator intended for use in the Rx5C348A/B is recommended to have the CL value on the order of 6 to 9pF. Its oscillation frequency should be measured by the method described in " P.28  Measurement of Oscillation Frequency ". Any crystal oscillator found to have an excessively high or low oscillation frequency (causing a time count gain or loss, respectively) should be replaced with another one having a smaller and greater CL value, respectively until another one having an optimum CL value is selected. In this case, the bit settings disabling the oscillation adjustment circuit (see " P.30  Oscillation Adjustment Circuit") should be written to the oscillation adjustment register. Incidentally, the high oscillation frequency of the crystal oscillator can also be adjusted by adding an external oscillation stabilization capacitor CGOUT as illustrated in the diagram below.

Oscillator

Circuit

OSCIN

CG RD

OSCOUT

32kHz

CGOUT

*1) The CGOUT should have a capacitance ranging

from 0 to 15 pF.

Course (D) It is necessary to select the crystal oscillator in the same manner as in Course (C) as well as correct errors in the time count of each RTC in the same manner as in Course (B) by the method described in " P.30  Oscillation Adjustment Circuit ".

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Rx5C348A/B

Oscillation Adjustment Circuit  The oscillation adjustment circuit can be used to correct a time count gain or loss with high precision by varying the number of 1-second clock pulses once per 20 seconds. The oscillation adjustment circuit can be disabled by writing the settings of "*, 0, 0, 0, 0, 0, *" ("*" representing "0" or "1") to the F6, F5, F4, F3, F2, F1, and F0 bits in the oscillation adjustment circuit. Conversely, when such oscillation adjustment is to be made, an appropriate oscillation adjustment value can be calculated by the equation below for writing to the oscillation adjustment circuit.

(1) When Oscillation Frequency (* 1) Is Higher Than Target Frequency (* 2) (Causing Time Count Gain) Oscillation adjustment value (*3) = (Oscillation frequency - Target Frequency + 0.1)

Oscillation frequency × 3.051 × 10

-6

≈ (Oscillation Frequency – Target Frequency) × 10 + 1

* 1) Oscillation frequency: Frequency of clock pulse output from the 32KOUT pin at normal temperature in the manner described

in " P.28  Measurement of Oscillation Frequency ". * 2) Target frequency: Desired frequency to be set. Generally, a 32.768-kHz crystal oscillator has such temperature

characteristics as to have the highest oscillation frequency at normal temperature. Consequently,

the crystal oscillator is recommended to have target frequency settings on the order of 32.768 to

32.76810 kHz (+3.05ppm relative to 32.768 kHz). Note that the target frequency differs depending

on the environment or location where the equipment incorporating the RTC is expected to be

operated. * 3) Oscillation adjustment value: Value that is to be finally written to the F0 to F6 bits in the Oscillation Adjustment Register and is

represented in 7-bit coded decimal notation.

(2) When Oscillation Frequency Is Equal To Target Frequency (Causing Time Count neither Gain nor Loss) Oscillation adjustment value = 0, +1, -64, or –63

(3) When Oscillation Frequency Is Lower Than Target Frequency (Causing Time Count Loss) Oscillation adjustment value = (Oscillation frequency - Target Frequency)

Oscillation frequency × 3.051 × 10

-6

≈ (Oscillation Frequency – Target Frequency) × 10 Oscillation adjustment value calculations are exemplified below (A) For an oscillation frequency = 32768.85Hz and a target frequency = 32768.05Hz

Oscillation adjustment value = (32768.85 - 32768.05 + 0.1) / (32768.85 × 3.051 × 10 ≈ (32768.85 - 32768.05) × 10 + 1 = 9.001 ≈ 9 In this instance, write the settings ((0),F6,F5,F4,F3,F2,F1,F0)=(0,0,0,0,1,0,0,1) in the oscillation adjustment register. Thus, an appropriate oscillation adjustment value in the presence of any time count gain represents a distance from 01h.

(B) For an oscillation frequency = 32762.22Hz and a target frequency = 32768.05Hz

Oscillation adjustment value = (32762.22 - 32768.05) / (32762.22 × 3.051 × 10 ≈ (32762.22 - 32768.05) × 10 = -58.325 ≈ -58 To represent an oscillation adjustment value of - 58 in 7-bit coded decimal notation, subtract 58 (3Ah) from 128 (80h) to obtain 46h. In this instance, write the settings of ((0),F6,F5,F4,F3,F2,F1,F0) = (0,1,0,0,0,1,1,0) in the oscillation adjustment register. Thus, an appropriate oscillation adjustment value in the presence of any time count loss represents a distance from 80h.

-6

)

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Rev.2.01 - 30 -

Rx5C348A/B

Notes:

1) Oscillation adjustment does not affect the frequency of 32.768-kHz clock pulses output from the 32KOUT pin.

2) If following 3 conditions are completed, actual clock adjustment value could be different from target adjustment value that set by oscillator adjustment function.

1. Using oscillator adjustment function

2. Access to Rx5C348A/B at random, or synchronized with external clock that has no relation to Rx5C348A/B, or synchronized with periodic interrupt in pulse mode.

3. Access to Rx5C348A/B more than 2 times per each second on average.

For more details, please contact to Ricoh.

How to evaluate the clock gain or loss  The oscillator adjustment circuit is configured to change time counts of 1 second on the basis of the settings of the oscillation adjustment register once in 20 seconds or 60 seconds. The oscillation adjustment circuit does not effect the frequency of 32768Hz-clock pulse output from the 32KOUT pin. Therefore, after writing the oscillation adjustment register, we cannot measure the clock error with probing 32KOUT clock pulses. The way to measure the clock error as follows:

(1) Output a 1Hz clock pulse of Pulse Mode with interrupt pin Set (0,0,x,x,0,0,1,1) to Control Register 1 at address Eh.

(2) After setting the oscillation adjustment register, 1Hz clock period changes every 20seconds ( or every 60 seconds) like next page figure.

1Hz clock pulse

T0 T0 T0 T1

1 time 19 times

Measure the interval of T0 and T1 with frequency counter. A frequency counter with 7 or more digits is recommended for the measurement.

(3) Calculate the typical period from T0 and T1 T = (19×T0+1×T1)/20 Calculate the time error from T.

Rev.2.01 - 31 -

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Rx5C348A/B

 Oscillation Halt Sensing, and Supply Voltage Monitoring

XSTP and VDET  The oscillation halt sensing circuit is configured to record a halt on oscillation by 32.768-kHz clock pulses. The supply voltage monitoring circuit is configured to record a drop in supply voltage below a threshold voltage of 2.1 or 1.6v. Each function has a monitor bit. I.e. XSTP bit is for the oscillation halt sensing circuit, and VDET is for the supply voltage monitoring circuit. XSTP and VDET bits are activated to “H”. The XSTP and VDET accept only the writing of 0. The XSTP bit is set to 1, when VDD power-up from 0V, but VDET is set to 0. The functions of these two monitor bits are shown in the table below. Oscillation Halt Sensing Circuit operates only when CE pin is Low. Sensing result is maintained after CE pin changes from “L” to “H”.

XSTP VDET Conditions of supply voltage and oscillation

0 0 No drop in supply voltage below threshold voltage and no halt in oscillation 0 1 Drop in supply voltage below threshold voltage and no halt in oscillation 1 * Halt on oscillation

VDD

32768Hz Oscillation

Threshold voltage (2.1v or 1.6v)

Oscillation halt

sensing flag (XSTP)

Supply voltage

monitor flag (VDET)

Internal initialization

period (1 to 2 sec.)

VDET←0 XSTP←0

VDET←0

Internal initialization

period (1 to 2 sec.)

VDET←0 XSTP←0

When the XSTP bit is set to 1 in the control register 2, the (0), F6 to F0, WALE, DALE, /12⋅24, /CLEN2, TEST, CT2, CT1, CT0, VDSL, VDET, /CLEN1, CTFG, WAFG, DAFG, SCRATCH1/2/3 bits are reset to 0 in the oscillation adjustment register, the control register 1, and the control register 2.

< Considerations in Using Oscillation Halt Sensing Circuit > Be sure to prevent the oscillation halt sensing circuit from malfunctioning by preventing the following:

1) Instantaneous power-down on the VDD

2) Condensation on the crystal oscillator

3) On-board noise to the crystal oscillator

4) Applying to individual pins volt age exceeding their respective maximum ratings In particular, note that the XSTP bit may fail to be set to 0 in the presence of any applied supply voltage as

illustrated below in such events as backup battery installation. Further, give special considerations to prevent excessive chattering in the oscillation halt sensing circuit.

VDD

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Rev.2.01 - 32 -

Rx5C348A/B

(

)

(

)

Voltage Monitoring Circuit  The supply monitoring circuit is configured to conduct a sampling operation during an interval of 7.8ms per second to check for a drop in supply voltage below a threshold voltage of 2.1 or 1.6v for the VDSL bit setting of 0 (the default setting) or 1, respectively, in the Control Register 2, thus minimizing supply current requirements as illustrated in the timing chart below. This circuit suspends a sampling operation once the VDET bit is set to 1 in the Control Register 2. The supply voltage monitor is useful for back-up battery checking.

Sampling timing for

VDD supply voltage

D6 in Address Fh

VDD

XSTP

VDET

Internal initialization period

1 to 2sec.

XSTP←0 VDET←0

2.1v or 1.6v

7.8ms

VDET←0

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Rev.2.01 - 33 -

Rx5C348A/B

 Alarm and Periodic Interrupt

The Rx5C348A/B incorporates the alarm interrupt circuit and the periodic interrupt circuit that are configured to generate alarm signals and periodic interrupt signals for output from the /INTR pin as described below.

(1) Alarm Interrupt Circuit The alarm interrupt circuit is configured to generate alarm signals for output from the /INTR, which is driven low (enabled) upon the occurrence of a match between current time read by the time counters (the day-of-week, hour, and minute counters) and alarm time preset by the alarm registers (the Alarm_W registers intended for the day-of-week, hour, and minute digit settings and the Alarm_D registers intended for the hour and minute digit settings).

(2) Periodic Interrupt Circuit The periodic interrupt circuit is configured to generate either clock pulses in the pulse mode or interrupt signals in the level mode for output from the /INTR pin depending on the CT2, CT1, and CT0 bit settings in the control register 1.

The above two types of interrupt signals are monitored by the flag bits (i.e. the WAFG, DAFG, and CTFG bits in the Control Register 2) and enabled or disabled by the enable bits (i.e. the WALE, DALE, CT2, CT1, and CT0 bits in the Control Register 1) as listed in the table below.

Flag bits Enable bits

Alarm_W WAFG

(D1 at Address Fh)

Alarm_D DAFG

(D0 at Address Fh)

Peridic interrupt CTFG

(D2 at Address Fh)

* At power-on, when the WALE, DALE, CT2, CT1, and CT0 bit s are set to 0 in the Control Register 1, the /INTR pin is driven high (disabled). * When two types of interrupt signals are output simultaneously from the /INTR pin, the output from the /INTR pin becomes an OR waveform of their negative logic.

Example: Combined Output to /INTR Pin Under Control of /ALARM_D and Periodic Interrupt

WALE (D7 at Address Eh) DALE (D6 at Address Eh) CT2=CT1=CT0=0 (These bit setting of “0” disable the Periodic Interrupt) (D2 to D0 at Address Eh)

/Alarm_D

Periodic Interrupt

In this event, which type of interrupt signal is output from the /INTR pin can be confirmed by reading the DAFG, and CTFG bit settings in the Control Register 2.

Alarm Interrupt  The alarm interrupt circuit is controlled by the enable bits (i.e. the WALE and DALE bits in the Control Register 1) and the flag bits (i.e. the WAFG and DAFG bits in the Control Register 2). The enable bits can be used to enable this circuit when set to 1 and to disable it when set to 0. When intended for reading, the flag bits can be used to monitor alarm interrupt signals. When intended for writing, the flag bits will cause no event when set to 1 and will drive high (disable) the alarm interrupt circuit when set to 0. The enable bits will not be affected even when the flag bits are set to 0. In this event, therefore, the alarm interrupt circuit will continue to function until it is driven low (enabled) upon the next occurrence of a match between current time and preset alarm time.

/INTR

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Rev.2.01 - 34 -

Rx5C348A/B

←

The alarm function can be set by presetting desired alarm time in the alarm registers (the Alarm_W Registers for the day-of-week digit settings and both the Alarm_W Registers and the Alarm_D Registers for the hour and minute digit settings) with the WALE and DALE bits once set to 0 and then to 1 in the Control Register 1. Note that the WALE and DALE bits should be once set to 0 in order to disable the alarm interrupts circuit upon the coincidental occurrence of a match between current time and preset alarm time in the process of setting the alarm function.

Interval (1min.) during which a match between current time and preset alarm time occurs

/INTR

WALE←1 (DALE)

current time = preset alarm time

WALE (DALE)

WALE←1

(DALE)

WAFG←0 (DAFG)

current time = preset alarm time

After setting WALE(DALW) to 0, Alarm registers is set to current time, and WALE(DALE) is set to 1, /INTR will be not driven to “L” immediately, /INTR will be driven to “L” at next alarm setting time.

Periodic Interrupt  Setting of the periodic selection bits (CT2 to CT0) enables periodic interrupt to the CPU. There are two waveform modes: pulse mode and level mode. In the pulse mode, the output has a waveform duty cycle of around 50%. In the level mode, the output is cyclically driven low and, when the CTFG bit is set to 0, the output is return to High (OFF).

CT2 CT1 CT0

Description

Wave form mode Interrupt Cycle and Falling Timing 0 0 0 - OFF(H) (Default) 0 0 1 - Fixed at “L” 0 1 0 Pulse Mode *1) 2Hz(Duty50%) 0 1 1 Pulse Mode *1) 1Hz(Duty50%) 1 0 0 Level Mode *2) Once per 1 second (Synchronized with

Second counter increment)

1 0 1 Level Mode *2) Once per 1 minute (at 00 seconds of every

Minute)

1 1 0 Level Mode *2) Once per hour (at 00 minutes and 00

Seconds of every hour)

1 1 1 Level Mode *2) Once per month (at 00 hours, 00 minutes,

and 00 seconds of first day of every month)

*1) Pulse Mode: 2-Hz and 1-Hz clock pulses are output in synchronization with the increment of the second counter as

illustrated in the timing chart below.

CTFG Bit

/INTR Pin

pprox. 92µs

(Increment of second counter)

Rewriting of the second counter

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Rev.2.01 - 35 -

Rx5C348A/B

In the pulse mode, the increment of the second counter is delayed by approximately 92 µs from the

*2) Level Mode: Periodic interrupt signals are output with selectable interrupt cycle settings of 1 second, 1 minute, 1

hour, and 1 month. The increment of the second counter is synchronized with the falling edge of periodic interrupt signals. For example, periodic interrupt signals with an interrupt cycle setting of 1 second are output in synchronization with the increment of the second counter as illustrated in the timing chart below.

CTFG Bit

/INTR Pin

Setting CTFG bit to 0

(Increment of second counter)

Setting CTFG bit to 0

*1), *2) When the oscillation adjustment circuit is used, the interrupt cycle will fluctuate once per 20sec. as

follows:

Pulse Mode: The “L” period of output pulses will increment or decrement by a maximum of

example, 1-Hz clock pulses will have a duty cycle of 50

±0.3784%.

Level Mode: A periodic interrupt cycle of 1 second will increment or decrement by a maximum of

±3.784ms. For

±3.784 ms.

32-kHz CLOCK OUTPUT 

For the Rx5C348A, 32.768-kHz clock pulses are output from the 32KOUT pin when either the /CLEN1 bit in the Control Register 2 or the /CLEN2 bit in the Control Register 1 is set to 0. When both the /CLEN1 and /CLEN2 bits are set to 0, the 32KOUT pin output is driven high (off).

/CLEN1

(D3 at Address Fh)

/CLEN2

(D4 at Address Eh)

32KOUT PIN

(N-channel Open Drain) 1 1 OFF(H) 0(Default) *

Clock pulses

* 0(Default)

The 32KOUT pin output is synchronized with the /CLEN1 and /CLEN2 bit settings as illustrated in the timing chart below.

/CLEN1or2

32KOUT PIN

Max.62.0µs

For the Rx5C348B, 32.768-kHz clock pulses are output from the 32KOUT pin regardless of such internal register settings.

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Rev.2.01 - 36 -

 Typical Applications

Typical Power Circuit Configurations 

Sample circuit configuration 1

OSCIN

System power supply

Rx5C348A/B

*1) Install bypass capacitors for high-frequency and low-frequency applications in parallel in close vicinity to the Rx5C348A/B.

OSCOUT

32768Hz

VDD

*1)

VSS

Sample circuit configuration 2

OSCIN

OSCOUT

VDD

32768Hz

System power supply

*1)

*1) When using an OR diode as a power supply fo

the Rx5C348A/B ensure that voltage exceeding the absolute maximum rating o VDD+0.3v is not applied the 32KOUT pin.

Primary

VSS

Battery

OSCIN

OSCOUT

VDD

VSS

32768Hz

System power supply

*1)

Secondary Battery

Rev.2.01 - 37 -

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Rx5C348A/B

Connection of /INTR and 32KOUT Pin  The /INTR pin follows the N-channel open drain output logic and contains no protective diode on the power supply side. As such, it can be connected to a pull-up resistor of up to 5.5v regardless of supply voltage. The 32KOUT pin follows the N-channel open drain output logic, too. However, it contains protective diode on the power supply side. As such, it cannot be connected to a pull-up resistor over VDD+0.3v. Such connection involves considerations for the supply current requirements of a pull-up resistor, which can be roughly calculated by the following equation:

I = 0.5 × (VDD or VCC) / Rp

/INTR or 32KOUT

OSCIN

OSCOUT

VSB

32768Hz

System power supply (VDD)

*1)

Backup power supply (VCC)

*1) Depending on whether the /INTR or 32KOU

pins are to be used during battery backup, it should be connected to a pull-up resistor at the following different positions:

(1) Position A in the left diagram when it is not to

be used during battery backup.

(2) Position B in the left diagram when it is to be

used during battery backup.

VSS

Connection of CE Pin  Connection of the CE pin requires the following considerations:

1) The CE pin is configured to enable the oscillation halt sensing circuit only when driven low. As such, it should be driven low or open at power-on from 0v.

2) The CE pin should also be driven low or open immediately upon the host going down (see "P.25



Considerations in Reading and Writing Time Data under special condition").

I/O

CONTROL

SCLK

VDD

Lower limit operating voltage for the CPU

Backup power supply

0.2×VDD

Min.0µs

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Min.0µsMin.0µs

Rev.2.01 - 38 -

Rx5C348A/B

Connection With 3-Wire Serial Interface Bus  To connect the Rx5C348A/B with 3-wire serial interface bus, shorten the SI and SO pins and connect them to the data line as shown in the figure below .

CE0

Host

CE1

SCL

DAT

SCLK SI

CE SCLK

SIO

Rx5C348A/B

The other Peripheral IC

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Rev.2.01 - 39 -

Rx5C348A/B

 Typical Characteristics

Test circuit

OSCOUT

VDD

OSCIN

32KOUT

VSS

32768Hz

Frequency

Counter

X’tal : 32.768kHz (R1=30k

Ω typ)

(CL=6pF to 8pF) Topt : 25

°C

Output pins : Open

Timekeeping Current vs. Supply voltage Timekeeping Current vs. Supply voltage (with no 32-kHz clock output) (with 32-kHz clock output) (CE=Open, Output=Open, Topt=25

0.8

0.6

0.4

0.2

°C,Rx5C348A) (CE=Open, Output=Open,Topt=25°C)

1.5

Rx5C348A

0.5

Rx5C348B

Timekeeping Current IDD (uA)

0123456

Supply Voltage VDD(v)

Timekeeping Current IDD(uA)

0123456

Supply Voltage VDD(v)

CPU Access Current vs. SCLK Clock Frequency Timekeeping Current vs. Operating Temperature (Output=Open, Topt=25

°C) (with no 32-kHz clock output)

(CE=Open, Output=Open)

50 40 30 20

VDD=5v

CPU Access Current IDD(uA)

0 500 1000 1500 2000

SCLK Clock Frequency (kHz)

VDD=3v

1.5

0.5

Timekeeping Current IDD(uA)

-60 -40 -20 0 20 40 60 80 100 Operating Temperature Topt(

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Rev.2.01 - 40 -

Rx5C348A/B

Oscillation Frequency Deviation vs. External CG Oscillation Frequency Deviation vs. Supply Voltage (VDD=3v,Topt=25 External CG=0pF as standard)

°C, (Topt=25°C,VDD=3v as standard)

Oscillation Frequency Devitation

5 0

-5

-10

-15

(ppm)

-20

-25

-30

-35

-40 0 5 10 15 20

External CG (pF)

5 4 3 2 1 0

-1

-2

Devitation (ppm)

-3

Oscillation Frequency

-4

-5 0123456

Supply Voltage VDD(v)

Oscillation Frequency Deviation vs. Operating Temperature Oscillation Start Time vs. Supply Voltage

(VDD=3v , Topt=25

-20

-40

-60

-80

-100

Devitation (ppm)

-120

Oscillation Frequency

-140

°C external CG=0pF as standard) (Topt=25°C)

500

-60 -40 -20 0 20 40 60 80 10

Operating Temperature Topt(

400 300 200 100

Oscillation Start Time (ms)

0123456

Supply Voltage VDD(v)

VOL vs. IOL VOL vs. IOL (32KOUT Pin of the Rx5C348A and /INTR Pin) (32KOUT Pin of the Rx5C348B) (Topt=25

°C) (Topt=25°C)

30 25 20 15

IOL (mA)

5 0

0 0.2 0.4 0.6 0.8 1

VDD=5v

VOL (v)

VDD=3v

8 6 4

IOL (mA)

2 0

Rev.2.01 - 41 -

VDD=5v

VDD=3v

0 0.2 0.4 0.6 0.8 1

VOL (v)

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Rx5C348A/B

 Typical Software-based Operations

Initialization at Power-on 

Start

*1)

Power-on

*2)

XSTP=1?

Yes

Set Oscillation Adjustment

*4)

VDET=0?

Yes

*3)

Warnin g B a ck -u p

Batter

Run-down

*1) After power-on from 0 volt, the start of oscillation and the process of internal initialization require a

time span on 1to 2seconds, so that access should be done after the lapse of this time span or more.

*2) The XSTP bit setting of 0 in the Control Register 1 indicates power-on from backup battery and not

from 0v. For further details, see "P.32

 XSTP and VDET".

*3) This step is not required when the supply voltage monitoring circuit is not used. *4) This step involves ordinary initialization including the Oscillation Adjustment Register and interrupt

cycle settings, etc.

Writing of T ime and Calendar Data 

CE ← H

Write to Time Counter and

Calendar Counter

CE ← L

*1)

*2)

*3)

*1) When writing to clock and calendar counters, do not drive CE to “L” until

all times from second to year have been written to prevent error in writing time. (Detailed in "P.24

Time Data under special condition

*2) Any writing to the second counter will reset divider units lower than the

second digits.

*3) Take care so that process from CE driving to “H” to driving to “L” will be

complete within 1.0sec. (Detailed in "P.24

frequency

The Rx5C348A/B may also be initialized not at power-on but in the

process of writing time and calendar data.

 Considerations in Reading and Writing



djustment of Oscillation

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Rev.2.01 - 42 -

Reading Time and Calendar Dat a 

(1) Ordinary Process of Reading Time and Calendar Dat a

CE ← H

Read from Time Counter

and Calendar Counter

CE ← L

*1)

*2)

*1) When writing to clock and calendar counters, do not insert Stop Condition

until all times from second to year have been written to prevent error in writing time. (Detailed "P.24

Time Data under special condition

*2) Take care so that process from Start Condition to Stop Condition will be

complete within 0.5sec. (Detailed in "P.24

Reading and Writing Time Data under special condition".

Rx5C348A/B

 Considerations in Reading and Writing

 Considerations in

(2) Basic Process of Reading Time and Calendar Dat a with Periodic Interrupt Function

Set Periodic Interrupt

Cycle Selection Bits

Generate Interrupt in CPU

CTFG=1?

Yes

Read from Time Counter

and Calendar Counte

*2)

*1)

Other Interrupt

Processes

*1) This step is intended to select the level mode as a

waveform mode for the periodic interrupt function. *2) This step must be completed within 1.0 second. *3) This step is intended to set the CTFG bit to 0 in the

Control Register 2 to cancel an interrupt to the CPU.

*3)

Control Register 2

←(X1X1X011)

Rev.2.01 - 43 -

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Rx5C348A/B

(3) Applied Process of Reading Time and Calendar Data with Periodic Interrupt Function Time data need not be read from all the time counters when used for such ordinary purposes as time count indication. This applied process can be used to read time and calendar data with substantial reductions in the load involved in such reading.

For Time Indication in "Day-of-Month, Day-of-week, Hour, Minute, and Second" Format:

Control Register 1←

(XXXX0100)

Control Register 2←

(X1X1X011)

Generate interrupt to CPU

CTFG=1?

Yes

*2)

Sec.=00?

*1)

Other interrupts

Processes

*1) This step is intended to select the level

mode as a waveform mode for the periodic interrupt function.

*2) This step must be completed within 1.0

sec.

*3) This step is intended to read time data

from all the time counters only in the first session of reading time data afte writing time data.

*4) This step is intended to set the CTFG

bit to 0 in the Control Register 2 to cancel an interrupt to the CPU.

Read Min.,Hr.,Day,

and Day-of-week

Control Register 2←

(X1X1X011)

Yes

*3)

Use previous Min.,Hr.,

Day, and Day-of-week data

*4)

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Rev.2.01 - 44 -

Interrupt Process 

(1) Periodic Interrupt

Set Periodic Interrupt

Cycle Selection Bits

Generate Interrupt to CPU

*1)

Rx5C348A/B

*1) This step is intended to select the level mode as a

waveform mode for the periodic interrupt function.

*2) This step is intended to set the CTFG bit to 0 in

the Control Register 2 to cancel an interrupt to the CPU.

CTFG=1?

Yes

Conduct

Periodic Interru

Control Register 2←

(X1X1X011)

(2) Alarm Interrupt

WALE or DALE←0

Set Alarm Min., Hr., and

Day-of-week Registers

WALE or DALE←1

*2)

*1)

*2)

Other Interrupt

Processes

*1) This step is intended to once disable the alarm

interrupt circuit by setting the WALE or DALE bits to 0 in anticipation of the coincidental occurrence of a match between current time and preset alarm time in the process of setting the alarm interrupt function.

*2) This step is intended to enable the alarm interrupt

function after completion of all alarm interrupt settings.

*3) This step is intended to once cancel the alarm

interrupt function by writing the settings of "X,1,X, 1,X,1,0,1" and "X,1,X,1,X,1,1,0" to the Alarm_W Registers and the Alarm_D Registers, respectively.

Generate Interrupt to CPU

WAFG or DAFG=1?

Yes

Conduct Alarm Interrupt

Other Interrupt

Processes

*3)

Control Register 2 ←

(X1X1X101)

Rev.2.01 - 45 -

12345

RICOHCOMPANY,LTD.

ElectronicDevicesCompany

●Shin-Yokohamaoﬃce(InternationalSales)

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1.Theproductsandtheproductspeciﬁcationsdescribedinthisdocumentaresubjecttochangeor discontinuationofproductionwithoutnoticeforreasons

suchasimprovement.Therefore,before decidingtousetheproducts,pleaserefertoRicohsalesrepresentativesforthelatest informationthereon.

2.Thematerialsinthisdocumentmaynotbecopiedorotherwisereproducedinwholeorinpart withoutpriorwrittenconsentofRicoh.

3.Pleasebesuretotakeanynecessaryformalitiesunderrelevantlawsorregulationsbefore exportingorotherwisetakingoutofyourcountrytheproductsorthetechnicalinformation describedherein.

4.Thetechnicalinformationdescribedinthisdocumentshowstypicalcharacteristicsofand exampleapplicationcircuitsfortheproducts.Thereleaseofsuchinformationisnottobe construedasawarrantyoforagrantoflicenseunderRicoh'soranythirdparty'sintellectual propertyrightsoranyotherrights.

5.

Theproductslistedinthisdocumentareintendedanddesignedforuseasgeneralelectronic componentsinstandardapplications(oﬃceequipment,telecommunicationequipment, measuringinstruments,consumerelectronicproducts,amusementequipmentetc.).Those customersintendingtouse

aproductinanapplicationrequiringextremequalityandreliability, forexample,inahighlyspeciﬁcapplicationwherethefailureormisoperationoftheproduct couldresultinhumaninjuryordeath(aircraft,spacevehicle,nuclearreactorcontrolsystem, traﬃccontrolsystem,automotiveand

transportationequipment,combustionequipment,safety

devices,lifesupportsystemetc.)shouldﬁrstcontactus.

6.Wearemakingourcontinuouseﬀorttoimprovethequalityandreliabilityofourproducts,but semiconductorproductsarelikelytofailwithcertainprobability.Inordertopreventanyinjuryto personsordamagestopropertyresultingfromsuchfailure,customersshouldbecarefulenough toincorporatesafetymeasuresintheirdesign,suchasredundancyfeature,ﬁrecontainment featureandfail-safefeature.Wedonotassumeanyliability

orresponsibilityforanylossor

damagearisingfrommisuseorinappropriateuseoftheproducts.

7.Anti-radiationdesignisnotimplementedintheproductsdescribedinthisdocument.

8.

PleasecontactRicohsalesrepresentativesshouldyouhaveanyquestionsorcomments concerningtheproductsorthetechnicalinformation.

RICOHCOMPANY.,LTD.ElectronicDevicesCompany

■

Ricoh presen ted wi th the Japan Manag ement Qualit y Award fo r 1999

Ricoh con tinually st rives to promote cu stomer sa tisfaction, and shares the achievements of its ma nagement q uality imp rovement program with people and society.

■R ic oh awa rded I SO 1 4001 cer tif ic at ion .

The Ricoh Group was awa rded ISO 14 001 cer tification, which is an internat ional standard for environm ental managem ent s ystems, at both its domestic and overseas prod uction facilit ies. Our cur rent ai m is to obtain ISO 14 001 cer tification for all of our bu sines s offices.

Ricoh com pleted the organizat ion of the Lead-fr ee product ion for all of our p roducts.

After Apr. 1, 200 6, we will ship out the lead free products only. Thus, all products that

will be shipped from now on comply with RoHS Directive.

RICOH Rx5C348A, Rx5C348B Technical data

Specifications and Main Features

Frequently Asked Questions

User Manual