SM8577B Datasheet, PDF (8/10 Pages) Nippon Precision Circuits Inc – Real-time Clock IC

SM8577B
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.
Second ( 0 to 59 )
MSB
LSB
FDT
s40
s20
s10
s8
s4
s2
s1
Minute ( 0 to 59 )
∗
mi40
mi20
mi10
mi8
mi4
mi2
mi1
Hour ( 0 to 23 )
∗
∗
h20
h10
h8
h4
h2
h1
Week ( 1 to 7 )
FSEL
W4
W2
W1
Day ( 1 to 31 )
∗
∗
d20
d10
d8
d4
d2
d1
Month ( 1 to 12 )
TM
∗
∗
mo10
mo8
mo4
mo2
mo1
Year ( 0 to 99 )
y80
y40
y20
y10
y8
y4
y2
y1
* 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.
NIPPON PRECISION CIRCUITS—8