DS1670 Datasheet, PDF (4/16 Pages) Dallas Semiconductor – Portable System Controller

DS1670
POWER-UP/POWER-DOWN CONSIDERATIONS
The DS1670 was designed to operate with a power supply of 3.3V. When 3.3V are applied within
nominal limits, the device becomes fully accessible after t_RPU (250ms typical). Before t_RPU elapses, all
inputs are disabled. When V_CC drops below 2.88V (typical), the RST pin is driven low. When V_CC drops
below the lower of 2.7V (typical) or the battery voltage, the device is switched over to the backup power
supply.
During power-up, when V_CC returns to an in-tolerance condition, the RST pin is kept in the active state
for 250ms (typical) to allow the power supply and microprocessor to stabilize.
ADDRESS/COMMAND BYTE
The command byte for the DS1670 is shown in Figure 2. Each data transfer is initiated by a command
byte. Bits 0 through 6 specify the addresses of the registers to be accessed. The MSB (bit 7) is the
Read/Write bit. This bit specifies whether the accessed byte will be read or written. A read operation is
selected if bit 7 is a 0 and a write operation is selected if bit 7 is a 1. The address map for the DS1670 is
shown in Figure 3.
ADDRESS/COMMAND BYTE Figure 2
76543 2 1 0
RD
A6 A5 A4 A3 A2 A1 A0
WR
DS1670 ADDRESS MAP Figure 3
BIT 7
BIT 0
00 0
10 SECONDS
SECONDS
01 0
10 MINUTES
MINUTES
02
0
12
24
10 HR
A/P
10 HR
HOURS
03 0
0
0
0
0
DAY
04 0
0
10 DATE
DATE
05 0
0
0
10
MONTH
MO.
06
10 YEAR
YEAR
07 M
10 SEC ALARM
SECONDS ALARM
08 M
10 MIN ALARM
MINUTES ALARM
09
M
12
24
10 HR
A/P
10 HR
HOUR ALARM
0A M 0
0
0
DAY ALARM
0B
CONTROL REGISTER
0C
STATUS REGISTER
0D
WATCHDOG REGISTER
0E
ADC REGISTER
0F
7F
RESERVED
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