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

SM8577B
When CE is HIGH, data write mode starts from the
first rising edge of CLK for which DATA is HIGH.
Valid data is then input on DATA from the 9th rising
edge of CLK. Time and date data is loaded into the
shift register in sync with the rising edge of CLK,
starting with the seconds’ digit LSB. Data is loaded
and shifted in the sequence second, minute, hour,
week, day, and month. After 60 rising edges of CLK,
the shift register contents are then transferred to the
timer counters.
Note that a data write cycle must contain 60 bits of
input data. If CE goes LOW before 60 bits are input,
the input data is invalid. If the input data exceeds 60
bits, data from the 61st bit is ignored (the first 60 bits
remain valid).
Supply Voltage Detection
The supply voltage detector tests the level of the
supply voltage once every 0.5 seconds. If the supply
voltage falls below the detector threshold, the FDT
bit is set to 1. The FDT bit is reset to 0 after a data
During a data write cycle, timer counter operation
stops on the first falling edge of CLK, and the 1 Hz
to 128 Hz frequency divider step counters are reset.
The 1 s counter increment signal is stopped and does
not restart until CE goes LOW. The divider step
counters are reset during the interval between the
first falling edge of CLK and the 2nd rising edge of
CLK.
The data write cycle should be completed within
t_CE ≤ 0.9 s.
If a data read cycle occurs immediately after a data
write cycle, a wait time (t_RCV) is required after CE
goes LOW.
Note that activating a read cycle when no valid data
is present will cause incorrect operation. All bits
must be valid data bits.
read cycle that contains at least 56 data bits. The
FDT bit is not reset for data read cycles of 55 bits or
less.
VDD
Detected Pulse
VDET
0.5 second
0.5 second
CE
(READ MODE)
FDT bit
NIPPON PRECISION CIRCUITS INC. reserves the right to make changes to the products described in this data sheet in order to
improve the design or performance and to supply the best possible products. Nippon Precision Circuits Inc. assumes no responsibility for
the use of any circuits shown in this data sheet, conveys no license under any patent or other rights, and makes no claim that the circuits
are free from patent infringement. Applications for any devices shown in this data sheet are for illustration only and Nippon Precision
Circuits Inc. makes no claim or warranty that such applications will be suitable for the use specified without further testing or modification.
The products described in this data sheet are not intended to use for the apparatus which influence human lives due to the failure or
malfunction of the products. Customers are requested to comply with applicable laws and regulations in effect now and hereinafter,
including compliance with export controls on the distribution or dissemination of the products. Customers shall not export, directly or
indirectly, any products without first obtaining required licenses and approvals from appropriate government agencies.
NIPPON PRECISION CIRCUITS INC.
NIPPON PRECISION CIRCUITS INC.
4-3, Fukuzumi 2 chome
Koto-ku, Tokyo 135-8430, Japan
Telephone: [phone]
Facsimile: 03-3642-6698
NC9617AE 1997.04
NIPPON PRECISION CIRCUITS—10