Epson RTC-72423, RTC-72421 B, RTC-72421 A, RTC-72423 A User Manual

MQ162-03

Application Manual

Real Time Clock Module

RTC-72421/72423

Model	Product Number
RTC-72421 A	Q4272421x000100
RTC-72421 B	Q4272421x000200
RTC-72423 A	Q4272423x000600
RTC-72423	Q4272423x000700

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RTC - 72421 / 72423

	CONTENTS
Overview .............................................................................................		1
Block diagram .....................................................................................		1
Terminal connections..........................................................................		2
Terminal functions...............................................................................		3
Characteristics ....................................................................................		4
1.	Absolute maximum ratings........................................................................................	4
2.	Recommended operating conditions.........................................................................	4
3.	Frequency characteristics and current consumption characteristics..........................	4
4.	Electrical characteristics ( DC characteristics ) .........................................................	4
Switching characteristics (AC characteristics) ...........................................		5
1.	When ALE is used ....................................................................................................	5
2.	When ALE is fixed at VDD .........................................................................................	6
Registers.............................................................................................		7
1.	Register table............................................................................................................	7
2.	Notes ........................................................................................................................	7
3.	Functions of register bits (overview)..........................................................................	7
4.	Setting the fixed-period pulse output mode and fixed-period interrupt mode.............	8
5.	Resetting the fixed-period pulse output mode and fixed-period interrupt mode.........	8
Register description ............................................................................		9
1.	Timing registers ........................................................................................................	9
2.	CD register (control register D) ...............................................................................	10
3.	CE register (control register E)................................................................................	11
4.	CF register (control register F) ................................................................................	13
Using the RTC-72421/RTC-72423 .....................................................		14
1.	Power-on procedure (initialization) ..........................................................................	14
2.	Read/write of S1 to W registers ..............................................................................	16
3.	Write to 30-second ADJ bit .....................................................................................	16
4.	Using the CS1 pin ...................................................................................................	17
Power supply circuit example.............................................................		17
Examples of connection to general-purpose microprocessor.............		18
External dimensions...........................................................................		19
Marking layout....................................................................................		19
Reference data ..................................................................................		20
Application notes................................................................................		21
1.	Notes on handling ...................................................................................................	21
2.	Notes on packaging ................................................................................................	21

RTC - 72421 / 72423

4-BIT PARALLEL INTERFACE REAL TIME CLOCK MODULE

RTC - 72421 / 72423

•Built-in crystal unit removes need for adjustment and reduces installation costs

•Microprocessor bus compatible ( tWW, tRD = 120 ns )

•Use of C-MOS IC enables low current consumption ( 5 A Max., at VDD = 2.0 V )

•Compatibility with Intel CPU bus

•Address latch enable (ALE) pin compatible with multiplex bus CPUs

•Time (hours, minutes, seconds) and calendar (year, month, day) counter

•24-hour/12-hour switchover and automatic leap-year correction functions

•Fixed-period interrupt function

•30-seconds correction (adjustment) function

•Stop, start, and reset functions

•Battery back-up function

•Same mounting conditions as general-purpose SMD ICs possible (RTC-72423)

Pins and functions compatible with the SMC-5242 series

Overview

The RTC-72421/RTC-72423 module is a real time clock that can be connected directly to a microprocessor's bus. Its built-in crystal unit enables highly accurate time-keeping with no physical access required for adjustment and, since there is no need to connect external components, mounting and other costs can be reduced.

In addition to its time and calendar functions, the RTC-72421/RTC-72423 enables the use of 30-seconds correction and fixedperiod interrupt functions.

The RTC-72421/RTC-72423 module is ideally suited for applications requiring timing management, such as personal computers, dedicated word-processors, fax machines, multi-function telephones, and sequencers.

Block diagram
							RTC-72421/72423
		OSC	Counter
D3		RESET	STOP		HOLD	BUSY
D2	Gate
		bit	bit		bit	bit		24/12
D1
		30sec ADJ						bit
D0
		bit
WR			S1	S10	MI1	MI10	H1	H10	W
	Gate
RD
A3		S1 to CF
A2			D1	D10	MO1	MO10	Y1	Y10
A1	Latch	Decoder
A0
CS0
									Output Selector
ALE									STD.P
								64 Hz
CS1
							1 Second carry
			CD		CE	CF	1 Minute carry
							1 Hour carry

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MQ - 162 - 03

RTC - 72421 / 72423

Terminal connections

					RTC-72421																RTC-72423
STD.P				1						18	VDD				STD.P			1							24		VDD
																		2						23		(VDD)
				2						17	(VDD)				CS0
	CS0														N.C.			3						22		(VDD)
ALE				3						16	(VDD)				ALE			4						21			N.C.
															A0			5						20			CS1
A0				4						15	CS1
															N.C.			6						19			D0
A1				5						14	D0				A1			7						18			N.C.
															N.C.			8						17			N.C.
A2				6						13	D1				A2			9						16			D1
A3				7						12	D2				A3			10						15			D2
															RD			11						14			D3
															GND			12						13
	RD			8						11	D3																WR
GND				9						10
												WR

The (VDD) pins are at the same electrical level as VDD. Do not connect these pins externally. The N.C. pins are not connected internally. Ground them in order to prevent noise.

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MQ - 162 - 03

RTC - 72421 / 72423

Terminal functions

Signal

Pin No.

Input/ou

Function

tput

RTC-72421

RTC-72423

Connect these pines to a bi-directional data bus or CPU data bus. Use this bus

to read to and write from the internal counter and registers.

CS1

CS0

RD

WR

Mode of D0 to D3

D0-D3

11−

14− 16, 19

Bi-

H

L

L

H

Output mode (read mode)

14

H

L

H

L

Input mode (write mode)

(Data bus)

direction

H

L

L

L

Do not use

L

H or L

High impedance (back-up mode)

H

H

H or L

High impedance (RTC not selected)

Address input pins used for connection to CPU address, etc. Used to select the

A0-A3

4−

7

5, 7, 9, 10

Input

RTC’s internal counter and registers (address selection).

(Address bus)

When the RTC is connected to a multiplexed-bus type of CPU, these pines can

also be used in combination with the ALE described below

Reads in address data and

state for internal latching.

CS0

When the ALE is high, the address data and

state is read into the RTC.

CS0

When the (through-mode) ALE falls, the address data and

state at that

CS0

ALE

point are held. The held address data and

status are maintained while

3

4

Input

CS0

(Address Latch Enable)

the ALE is low.

ALE

Address data and

CS0

status

H

Read into the RTC to set address data

L

Held in the RTC (latched at the trailing edge of the ALE)

If the RTC is connected to a CPU that does not have an ALE pin and thus there

is no need to use this ALE pin, fix it to VDD.

Writes the data on D0 to D3 into the register of the address specified by A0 to

WR

A3, at the leading edge of

.

10

13

Input

WR

(WRite)

Make sure that

RD

and

WR are never low at the same time.

Output data to D0 to D3 from the register at the address specified by A0 to A3,

RD

while

is

low.

8

11

Input

RD

(ReaD)

Make sure that

RD

and

WR are never low at the same time.

When CS1 is high and

is low, the RTC’s chip-select function is valid and

CS0

read and write are enabled.

When the RTC is connected to a multiplexed-bus type of CPU,

requires

CS1,

CS0

CS0

15,2

20,2

Input

the operation of the ALE (see the description of the ALE).

(Chip Select)

Use CS1 connected to a power voltage detection circuit. When CS1 is high, the

RTC is enabled; when it is low, the RTC is on standby.

When CS1 goes low, the HOLD and RESET bits in the RTC registers are

cleared to 0.

This is an N-channel open drain output pin.

Depending on the setting of the CE register, a fixed-period interrupt signal and a

pulse signal are output.

The output from this pin cannot be inhibited by the CS1 and

signals.

CS0

Use a load voltage that is less than or equal to VDD. If not using this pin, keep it

open-circuit.

An example of STD.P connection is shown below.

+5 V or VDD

STD.P

RTC

At least 2.2 kΩ

1

1

Output

(STanDard Pulse)

STD.P

If the STD.P output is not be used during standby operation, connecting the pull-

up resister to +5 V provides a reduction in current consumption. If the STD.P

output is to be used even during standby, connect the pull-up resistor to the

RTC’s VDD. In this case, the current consumption will be increased by the

amount of current flowing through the pull-up resistor.

VDD

18

24

Connect this pin to power source. Supply to 5 V ±

10 % to this pin during normal

operation; at least 2 V during battery back-up operation.

GND

9

12

Connect this pin to ground.

(VDD)

16, 17

22,23

These pins are connected internally to VDD. Leave them open circuit.

N.C.

−

3, 6, 8,

These pins are not connected internally. Ground them.

17, 18, 21

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MQ - 162 - 03

RTC - 72421 / 72423

Characteristics

1. Absolute maximum ratings

Item

Symbol

Condition

Specification

Unit

Supply voltage

VDD

Ta=+25 ° C

− 0.3

to

7.0

V

Input voltage

VI

Ta=+25 ° C

GND− 0.3

to

VDD+0.3

V

Output voltage

VO

Ta=+25 ° C

GND− 0.3

to

VDD+0.3

V

Storage temperature

TSTG

RTC-72421

− 55

to

+85

° C

RTC-72423

− 55

to

+125

° C

2. Recommended operating conditions

Item

Symbol

Condition

Specification

Unit

Supply voltage

VDD

4.5

to

5.5

V

Operating temperature

TOPR

No condensation

RTC-72421 ; −

10 to +70

° C

RTC-72423 ; − 40 to +85

° C

Data hold voltage

VDH

2.0

to

5.5

V

CS1 data hold time

tCDR

See the section on data

2.0 Min.

µ s

hold timing

Operation recovery time

tr

3. Frequency characteristics and current consumption characteristics

Item

Symbol

Condition

Specification

Unit

RTC-72421A

±

10

Frequency tolerance

∆ f/f0

Ta=+25 ° C

RTC-72421B

±

50

VDD=5.0 V

RTC-72423A

±

20

RTC-72423

±

50

×

-6

10

RTC-72421 : − 10 ° C to +70 ° C

+10 / − 120

(+25 ° C reference)

Operation temperature

RTC-72423 : − 40 ° C to +85 ° C

+10 / − 220

(+25 ° C reference)

Frequency voltage

Ta=+25 ° C

±

5 Max.

× 10-6 / V

characteristics

VDD=2.0 V to 5.5 V

Aging

fa

VDD=5.0 V, Ta=+25 ° C

±

5 Max.

× 10-6 / year

Drop test 3 times on a hard board from

Shock resistance

S.R.

0.75 m height, or 29400 m/s2 × 0.2 ms ×

±

10 Max.

×

10-6

1/2 sin wave × 3 directions

Current consumption

IDD1

Ta=+25 ° C, CS1=0 V

VDD=5.0 V

1.0 Typ.

10 Max.

µ A

IDD2

I/O currents excluded

VDD=2.0 V

0.9 Typ.

5 Max.

4. Electrical characteristics ( DC characteristics )

Item	Symbol	Condition	Applicable pins	Min.	Typ.	Max.	Unit
High input voltage 1	VIH1		All input pins except for	2.2			V
			CS1
Low input voltage 1	VIL1					0.8
High input voltage 2	VIH2	VDD=2.0 V to	CS1	4/5VDD			V
		5.5 V
Low input voltage 2	VIL2					1/5VDD
Input leakage current 1	ILK1		Input pins except for			1/-1	µ A
		VI=VDD/0 V	D0 to D3
Input leakage current 2	ILK2					10/-10
			D0 to D3
Low output voltage 1	VOL1	IOL=2.5 mA				0.4
High output voltage	VOH	IOH=-400 µ A		2.4			V
Low output voltage 2	VOL2	IOL=2.5 mA	STD.P			0.4
Off-state leakage current	IOFFLK	VI = VDD / 0 V				10/-10	µ A
Input capacitance	CI	Input	Input pins except for		10
			D0 to D3
		frequency					pF
Input-output capacitance	CI/O	1 MHz	D0 to D3 and STD.P		20

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MQ - 162 - 03

RTC - 72421 / 72423

Switching characteristics (AC characteristics)

1. When ALE is used

Write mode

( VDD=5 V ± 0.5 V,

RTC-72421;Ta=− 10 ° C to +70 ° C, RTC-72423;Ta=− 40 ° C to +85 ° C )

Item

Symbol

Condition

Min.

Max.

Unit

CS1 set-up time

tSU(CS1)

1000

Address set-up time before ALE

tSU(A-ALE)

50

Address hold time after ALE

th(ALE-A)

50

ALE pulse width

tw(ALE)

80

ALE set-up time before write

tSU(ALE-W)

0

Write pulse width

tw(W)

120

ns

ALE set-up time after write

tSU(W-ALE)

50

Data input set-up time before write

tSU(D-W)

80

Data input hold time after write

th(W-D)

10

CS1 hold time

th(CS1)

1000

Write recovery time

trec(W)

200

Read mode

( VDD=5 V ± 0.5 V,

RTC-72421;Ta=− 10 ° C to +70 ° C, RTC-72423;Ta=− 40 ° C to +85 ° C )

Item

Symbol

Condition

Min.

Max.

Unit

CS1 set-up time

tSU(CS1)

1000

Address set-up time before ALE

tSU(A-ALE)

50

Address hold time after ALE

th(ALE-A)

50

ALE pulse width

tw(ALE)

80

ALE set-up time before read

tSU(ALE-R)

0

ns

ALE set-up time after read

tSU(R-ALE)

50

Data output transfer time after read

tPZV(R-Q)

CL=150 pF

120

Data output floating transfer time after read

tPVZ(R-Q)

0

70

CS1 hold time

th(CS1)

1000

Read recovery time

trec(W)

200

(1) Write mode

VIH2

VIH2

CS1

tsu(CS1)

tsu(A-ALE)

th(ALE-A)

th(CS1)

A0 to A3	VIH1	VIH1
CS0	VIL1	VIL1
	tw(ALE)
VIH1	VIH1
ALE
		VIL1		VIL1
		tsu(ALE-W)	tw(W)	tsu(W-ALE)
		VIH1		VIH1
WR		VIL1		VIL1
			tsu(D-W)	th(W-D)
		VIH1		VIH1
D0 to D3
(Input)		VIL1		VIL1

(2) Read mode

	VIH2		VIH2
CS1
tsu(CS1)			th(CS1)
	tsu(A-ALE) th(ALE-A)
A0 to A3	VIH1	VIH1
CS0	VIL1	VIL1
	tw(ALE)
VIH1	VIH1
ALE
		VIL1	VIL1

	tsu(ALE-R)	tsu(R-ALE)
	VIH1	VIH1
RD	VIL1	VIL1
	tpzv(R-Q)	tpvz(R-Q)
	VIH1	VIH1
D0 to D3
(Input)	VIL1	VIL1

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MQ - 162 - 03