Rainbow Electronics DS1670 - Manual (Page 4)

DS1670
4 of 17
POWER-UP/POWER-DOWN CONSIDERATIONS
The DS1670 was designed to operate with a power supply of 3.3 volts. When 3.3 volts are applied within
nominal limits, the device becomes fully accessible after t
RPU
(250 ms typical). Before t
RPU
elapses, all
inputs are disabled. When V
CC
drops below 2.88 volts (typical), the RST pin is driven low. When V
CC
drops below the lower of 2.7 volts (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 250 ms (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
7 6 5 4 3 2 1 0
RD
WR
A6 A5 A4 A3 A2 A1 A0
DS1670 ADDRESS MAP Figure 3
BIT 7 BIT 0
00 0 10 SECONDS SECONDS
01 0 10 MINUTES MINUTES
10 HR
02 0
12
24 A/P
10 HR HOURS
03 0 0 0 0 0 DAY
04 0 0 10 DATE DATE
05 0 0 0 10
MO.
MONTH
06 10 YEAR YEAR
07 M 10 SEC ALARM SECONDS ALARM
08 M 10 MIN ALARM MINUTES ALARM
10 HR
09 M
12
24 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