SM8580 Nippon_Precision_Circuits America, SM8580 Datasheet - Page 12

• Manufacturer Part Number: SM8580
• Description: Real-time Clock ic
• Manufacturer: Nippon_Precision_Circuits America

Control Registers (All Banks, Register E (bits 2, 3) and F)
I
I
I
I
TEST bit
Factory test bit.
This bit should be set to 0. Take care when writing
to other E register bits not to accidentally write 1
to the TEST bit. Automatically resets to 0 when
power (VDD) is applied.
TEMP bit
When set to 1, it enables the temperature sensor
voltage output on pin VTEMP. When set to 0,
VTEMP is high impedance. Automatically resets
to 0 when power is applied.
Bank SEL bits
Bank select bits for read/write operations.
STOP bit
When set to 1, the clock 32Hz frequency divider
counter stops and is reset. When set to 0, the clock
restarts.
Bank SEL1
0, 1, 2
Bank
0
0
1
1
Bank SEL0
Address
0
1
0
1
E
F
Accessed bank
Bank 0
Bank 1
Bank 2
Bank 1
Bank SEL1
TEST
Bit 3
SM8580AM
I
Normal seconds digit carry
±30 seconds digit adjust (when ADJ is set to 1)
BUSY/ADJ bit
This bit functions as a BUSY function in read
mode, and as an ADJ function in write mode.
• ADJ function (±30 seconds adjust bit)
• BUSY function (second registers increment or
Bank SEL0
Setting ADJ bit to "1"
TEMP
The following processes are operated when a
logic 1 is written to ADJ, however a logic 0 can-
not be written to.
Second registers are reset to 00 and minute reg-
isters not incremented when the clock counter is
reset and the second registers are currently 00 to
29.
Second registers are reset to 00 and minute reg-
isters are incremented when the clock counter is
reset and the second registers are currently 30 to
59.
The ADJ bit is automatically reset to 0 a maxi-
mum of 244µs after it is set to 1.
±30 seconds adjust busy indicator bit)
When BUSY is 1, the counters are being
updated (incremented or reset). To read or write
to clock and calendar registers, the BUSY flag
has to be 0. If reading data when BUSY is set to
1, there is a possibility that incorrect (intermedi-
ate) data will be output.
BUSY is set to 1 under the following two cir-
cumstances.
Bit 2
NIPPON PRECISION CIRCUITS INC.—12
max 244µs
STOP
Bit 1
244µs
Carry complete
Adjust function
complete
BUSY/ADJ
Bit 0