DS1685 Maxim, DS1685 Datasheet - Page 18

• Manufacturer Part Number: DS1685
• Description: The DS1685/DS1687 are real-time clocks (RTCs) designed as successors to the industry-standard DS1285,DS1385, DS1485, and DS1585 PC RTCs
• Manufacturer: Maxim

Figure 5. DS1685/DS1687 Register Map and Extended Register Bank Definition
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
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. Bits in these locations cannot be written and return a 0 if read.
0D
0E
00
3F
7F
MSB
TIMEKEEPING AND CONTROL
50 BYTES-USER RAM
64 BYTES-USER RAM
BANK 0
= 0
DV0
LSB
0D
4C
4D
0E
4A
4B
4E
00
3F
40
41
42
43
44
45
46
47
48
49
4F
50
51
52
53
54
7F
MSB
18 of 34
EXTENDED CONTROL REG 4A
EXTENDED CONTROL REG 4B
TIMEKEEPING AND CONTROL
EXTENDED RAM DATA PORT
5
EXTENDED RAM ADDRESS
1
2
3
4
6
TH
ND
RD
5) Wake Up
6) Kickstart
7) RAM Clear Control/Status
8) 128 Bytes Extended RAM Access
ST
TH
TH
MODEL NUMBER BYTE
50 BYTES-USER RAM
BYTE SERIAL NUMBBER
BYTE SERIAL NUMBER
BYTE SERIAL NUMBER
BYTE SERIAL NUMBER
BYTE SERIAL NUMBER
BYTE SERIAL NUMBER
RTC ADDRESS-2
RTC ADDRESS-3
CENTURY BYTE
DATE ALARM
BANK 1
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
CRC BYTE
DS1685/DS1687 3V/5V Real-Time Clocks
1
DV0 =
LSB
EXTENDED
128 x 8
RAM