SM8580 datasheet(12/23 Pages) NPC

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SM8580AM

NIPPON PRECISION CIRCUITS—12

Control Registers (All Banks, Register E (bits 2, 3) and F)

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.

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)

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 244

µs after it is set to 1, and thus the

244

µs interval.

• BUSY function (second registers increment or

±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.

Bank

A d dress

Bit 3

Bit 2

Bit 1

Bit 0

0, 1, 2

TEST

TEMP

Bank SEL1

Bank SEL0

S T O P

B U SY/ADJ

Bank SEL1

Bank SEL0

Accessed bank

Bank 0

Bank 1

Bank 2

Bank 1

Normal seconds digit carry

±30 seconds digit adjust (when ADJ is set to 1)

Carry complete

244

µs

Adjust function

complete

max 244

µs

Setting ADJ bit to "1"

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