Datasheet

DS1685/DS1687 3V/5V Real-Time Clocks
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Figure 5. DS1685/DS1687 Register Map and Extended Register Bank Definition
MSB
BANK 0 DV0
= 0
LSB
MSB
BANK 1 DV0 =
1
LSB
00
TIMEKEEPING AND CONTROL
00
TIMEKEEPING AND CONTROL
0D
0D
0E
50 BYTES-USER RAM
0E
50 BYTES-USER RAM
3F
3F
7F
64 BYTES-USER RAM
40 MODEL NUMBER BYTE
41 1
ST
BYTE SERIAL NUMBER
42 2
ND
BYTE SERIAL NUMBER
43 3
RD
BYTE SERIAL NUMBER
44 4
TH
BYTE SERIAL NUMBER
45 5
TH
BYTE SERIAL NUMBBER
46 6
TH
BYTE SERIAL NUMBER
47
CRC BYTE
48
CENTURY BYTE
49
DATE ALARM
4A EXTENDED CONTROL REG 4A
4B EXTENDED CONTROL REG 4B
4C
RESERVED
4D
RESERVED
4E RTC ADDRESS-2
4F RTC ADDRESS-3
50
EXTENDED RAM ADDRESS
51 RESERVED
52 RESERVED
53
EXTENDED RAM DATA PORT
54
RESERVED
7F
When bank 1 is selected, the clock/calendar registers and the original 50 bytes of user RAM still appear as bank 0.
However, the registers that provide control and status for the extended functions are accessed in place of the
additional 64 bytes of user RAM. The major functions controlled by the extended registers are listed below:
1) 64-Bit Silicon Serial Number
2) Century counter
3) Date Alarm
4) Auxiliary Battery Control/Status
5) Wake Up
6) Kickstart
7) RAM Clear Control/Status
8) 128 Bytes Extended RAM Access
The bank selection is controlled by the state of the DV0 bit in register A. To access bank 0, the DV0 bit should be
written to a 0. To access bank 1, DV0 should be written to a 1. Register locations designated as reserved in the
bank 1 map are reserved for future use by Maxim Integrated. Bits in these locations cannot be written and return a
0 if read.
EXTENDED
RAM
128 x 8