Rainbow Electronics DS1647P User Manual

www.maxim-ic.com

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DS1647/DS1647P

Nonvolatile Timekeeping RAM

FEATURES

§ Integrates NV SRAM, real-time clock,

crystal, power-fail control circuit and lithium energy source

§ Clock registers are accessed identically to the

static RAM. These registers are resident in the eight top RAM locations

§ Totally nonvolatile with over 10 years of

operation in the absence of power

§ BCD coded year, month, date, day, hours,

minutes, and seconds with leap year compensation valid up to 2100

§ Power-fail write protection allows for ±10%

VCC power supply tolerance

§ DS1647 only (DIP Module)

- Standard JEDEC byte-wide 128k x 8

RAM pinout

§ DS1647P only (PowerCap® Module Board)

- Surface mountable package for direct

connection to PowerCap containing battery and crystal

- Replaceable battery (PowerCap)

- Power-fail output

- Pin-for-pin compatible with other

densities of DS164XP Timekeeping RAM

ORDERING INFORMATION

DS1647 32-pin DIP module *DS1647P 34-pin PowerCap Module

Board

*DS9034PCX PowerCap (Required; must

be ordered separately)

PIN ASSIGNMENT

NC A15 A16

PFO

DQ7 DQ6 DQ5 DQ4 DQ3 DQ2 DQ1 DQ0

GND

A18

A16 A14 A12

DQ0

DQ1

DQ2

GND

34-Pin PowerCap Module Board

(Uses DS9034PCX PowerCap)

2 3 4

11 12

32-Pin Encapsulated Package

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

X1 GND V 16 17

BAT

32 31

30 29

28 27

26 25

24 23

22 21

15 17

DQ7

DQ6

DQ5

DQ4

DQ3

34 33 32 31 30 29 28

27 26 25 24 23 22 21 20 19 18

18 17 14

3 2 1 0

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DS1647/DS1647P

PIN DESCRIPTION

A0-A18 - Address Input

CE - Chip Enable

OE - Output Enable

WE - Write Enable

- +5V

GND - Ground

DQ0-DQ7 - Data Input/Output NC - No Connection

PFO - Power-fail Output

(DS1647P only) X1, X2 - Crystal Connection V

- Battery Connection

BAT

DESCRIPTION

The DS1647 is a 512k x 8 nonvolatile static RAM with a full-function real-time clock, which are both accessible in a byte-wide format. The nonvolatile timekeeping RAM is functionally equivalent to any JEDEC standard 512k x 8 SRAM. The device can also be easily substituted for ROM, EPROM and EEPROM, providing read/write nonvolatility and the addition of the real-time clock function. The realtime clock information resides in the eight uppermost RAM locations. The RTC registers contain year, month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the day of the month and leap year are made automatically. The RTC clock registers are double-buffered to avoid access of incorrect data that can occur during clock update cycles. The double-buffered system also prevents time loss as the timekeeping countdown continues unabated by access to time register data. The DS1647 also contains its own power-fail circuitry, which deselects the device when the VCC supply is in an out-oftolerance condition. This feature prevents loss of data from unpredictable system operation brought on by low VCC as errant access and update cycles are avoided.

PACKAGES

The DS1647 is available in two packages: 32-pin DIP and 34-pin PowerCap module. The 32-pin DIP style module integrates the crystal, lithium energy source, and silicon all in one package. The 34-pin PowerCap Module Board is designed with contacts for connection to a separate PowerCap (DS9034PCX) that contains the crystal and battery. This design allows the PowerCap to be mounted on top of the DS1647P after the completion of the surface mount process. Mounting the PowerCap after the surface mount process prevents damage to the crystal and battery due to the high temperatures required for solder reflow. The PowerCap is keyed to prevent reverse insertion. The PowerCap Module Board and PowerCap are ordered separately and shipped in separate containers. The part number for the PowerCap is DS9034PCX.

CLOCK OPERATIONS - READING THE CLOCK

While the double-buffered register structure reduces the chance of reading incorrect data, internal updates to the DS1647 clock registers should be halted before clock data is read to prevent reading of data in transition. However, halting the internal clock register updating process does not affect clock accuracy. Updating is halted when a 1 is written into the read bit, the 7th most significant bit in the control register. As long as 1 remains in that position, updating is halted. After a halt is issued, the registers reflect the count, that is day, date, and time that was present at the moment the halt command was issued. However, the internal clock registers of the double-buffered system continue to update so that clock accuracy is not affected by the access of data. All of the DS1647 registers are updated simultaneously after the clock status is reset. Updating is within a second after the read bit is written to 0.

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BLOCK DIAGRAM DS1647 Figure 1

TRUTH TABLE DS1647 Table 1

5V ± 10%

<4.5V >V

BAT

CE OE WE

X X DESELECT HIGH-Z STANDBY

X X X DESELECT HIGH-Z STANDBY V V V

XVILWRITE DATA IN ACTIVE V V

V V

X X X DESELECT HIGH-Z CMOS STANDBY X X X DESELECT HIGH-Z DATA RETENTION

DS1647/DS1647P

MODE DQ POWER

READ DATA OUT ACTIVE READ HIGH-Z ACTIVE

MODE

SETTING THE CLOCK

The MSB Bit, B7, of the control register is the write bit. Setting the write bit to a 1, like the read bit halts updates to the DS1647 registers. The user can then load them with the correct day, date and time data in 24-hour BCD format. Resetting the write bit to a 0 then transfers those values to the actual clock counters and allows normal operation to resume.

STOPPING AND STARTING THE CLOCK OSCILLATOR

The clock oscillator may be stopped at any time. To increase the shelf life, the oscillator can be turned off

to minimize current drain from the battery. The OSC bit is the MSB for the second’s registers. Setting it to a 1 stops the oscillator.

FREQUENCY TEST BIT

Bit 6 of the day byte is the frequency test bit. When the frequency test bit is set to logic 1 and the oscillator is running, the LSB of the second’s register will toggle at 512 Hz. When the seconds register is being read, the DQ0 line will toggle at the 512 Hz frequency as long as conditions for access remain valid

CE low, OE low, and address for seconds register remain valid and stable).

(i.e.,

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DS1647/DS1647P

CLOCK ACCURACY (DIP MODULE)

The DS1647 is guaranteed to keep time accuracy to within ±1 minute per month at 25°C. The RTC is calibrated at the factory by Dallas Semiconductor using nonvolatile tuning elements, and does not require additional calibration. For this reason, methods of field clock calibration are not available and not necessary. Clock accuracy is also effected by the electrical environment and caution should be taken to place the RTC in the lowest level EMI section of the PCB layout. For additional information please see application note 58.

CLOCK ACCURACY (POWERCAP MODULE)

The DS1647 and DS9034PCX are each individually tested for accuracy. Once mounted together, the module will typically keep time accuracy to within ±1.53 minutes per month (35 ppm) at 25°C. Clock accuracy is also effected by the electrical environment and caution should be taken to place the RTC in the lowest level EMI section of the PCB layout. For additional information please see application note 58.

1646 REGISTER MAP - BANK1 Table 2

ADDRESS

7FFFF - - - - - - - - YEAR 00-99

7FFFE X X X - - - - - MONTH 01-12 7FFFD X X - - - - - - DATE 01-31 7FFFC X FT X X X - - - DAY 01-07 7FFFB X X - - - - - - HOUR 00-23 7FFFA X - - - - - - - MINUTES 00-59

7FFF9

OSC

-------

7FFF8WRXXXXXXCONTROLA

DATA

FUNCTION

SECONDS 00-59

OSC = STOP BIT

R = READ BIT FT = FREQUENCY TEST

W = WRITE BIT X = UNUSED

NOTE:

All indicated “X” bits are not dedicated to any particular function and can be used as normal RAM bits.

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