SM8577BS datasheet(8/10 Pages) NPC

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SM8577B

NIPPON PRECISION CIRCUITS—8

FUNCTIONAL DESCRIPTION

Timer Data Conﬁguration

Counter data is stored in BCD format. The IC

performs long/short month and leap-year adjustment

automatically. Leap-year adjustment occurs:

• when the decade digit is odd and the year digit

is a 2 or 6, and

• when the decade digit is even and the year digit

is a 0, 4 or 8.

The time display is 24-hour mode. All data is written

and read with the LSB ﬁrst.

* bits are don’t care write bits.

FDT is the supply voltage detect bit. FDT is set to 1

when the voltage between VDD and VSS falls below

1.7 ± 0.3 V. It is reset to 0 for data reads longer than

56 bits. Note that the FDT bit is not reset to 0 for

data reads of 55 bits or less. The read/write data bits

should initially be set to 0. After the supply voltage is

ﬁrst applied, the FDT bit should also be set to 0.

FSEL is the FOUT output frequency switch control

bit. 1 Hz output is selected when FSEL is 0, and 32

kHz output is selected when FSEL is 1. After power

is ﬁrst applied, 1 Hz default mode is selected.

TM is the factory test bit. It should be set to 0 for

normal use.

FDT

s40

s20

s10

∗

mi40

mi20

mi10

mi8

mi1

mi2

mi4

h20

h10

∗

FSEL

d20

d10

∗

mo10

mo8

mo1

mo2

mo4

∗

y80

y40

y20

y10

MSB

LSB

Second ( 0 to 59 )

Minute ( 0 to 59 )

Hour ( 0 to 23 )

Week ( 1 to 7 )

Day ( 1 to 31 )

Month ( 1 to 12 )

Year ( 0 to 99 )

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