app2740| Application Note

Application Note 2740
Accessing the DS1318 Clock Registers
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PIN CONFIGURATION
X1 X2 GND EXT A3 A2 A1 A0 DQ0 DQ1 DQ2 GND 1 2 3 4 5 6 7 8 9 10 11 12

DS1318

24 23 22 21 20 19 18 17 16 15 14 13

VCC VBAT IRQ SQW WE OE CE DQ7 DQ6 DQ5 DQ4 DQ3

DESCRIPTION
The DS1318 parallel-interface elapsed-time counter (ETC) is a 44-bit counter that can provide the elapsed time with 244ms resolution. The ETC has six registers. Four of the registers represent a 32-bit value in seconds. The other two registers use 12 bits to maintain the subsecond count (Table 1). The DS1318 can be used to track the time and date. A zero value in the ETC registers must be defined as some particular "zero epoch." In Unix systems, for example, the zero epoch is Midnight, January 1, 1970. The 32-bit seconds register can be used to represent any time between Midnight January 1, 1970, and 03:14:07 January 19, 2038. Conversion routines are normally used to convert the 32-bit count to a standard time and date format. Refer to Application Note 517: DS1371/DS1374 32-Bit Binary Counter Time Conversion at www.maxim-ic.com/app517. The DS1318 can also be used to count the elapsed time between two events.

Table 1. Address Map
ADDRESS 00H 01H 02H 03H 04H 05H 06H 07H 08H 09H 0AH 0BH 0CH BIT 7 SS3 SS11 S7 S15 S23 S31 ALM 7 ALM 15 ALM 23 ALM 31 TE PRS3 OSF BIT 6 SS2 SS10 S6 S14 S22 S30 ALM 6 ALM 14 ALM 22 ALM 30 ENOSC PRS2 UIP BIT 5 SS1 SS9 S5 S13 S21 S29 ALM 5 ALM 13 ALM 21 ALM 29 CCFG1 PRS1 0 BIT 4 SS0 SS8 S4 S12 S20 S28 ALM 4 ALM 12 ALM 20 ALM 28 CCFG0 PRS0 0 BIT 3 0 SS7 S3 S11 S19 S27 ALM 3 ALM 11 ALM 19 ALM 27 EPOL SRS3 0 BIT 2 0 SS6 S2 S10 S18 S26 ALM 2 ALM 10 ALM 18 ALM 26 SQWE SRS2 0 BIT 1 0 SS5 S1 S9 S17 S25 ALM1 ALM 9 ALM 17 ALM 25 PIE SRS1 PF BIT 0 SQWS SS4 S0 S8 S16 S24 ALM0 ALM 8 ALM 16 ALM 24 AIE SRS0 ALMF FUNCTION Subseconds0 Subseconds1 Seconds0 Seconds1 Seconds2 Seconds3 Alarm0 Alarm1 Alarm2 Alarm3 ControlA ControlB Status RANGE 00 F0h 00 FFh 00 FFh 00 FFh 00 FFh 00 FFh 00 FFh 00 FFh 00 FFh 00 FFh 00 FFh 00 FFh --

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