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iii.Frequency of STD.P pin output in fixed-period pulse output mode
In fixed-period pulse output mode, the timing of output is determined by the frequency of the internal crystal unit.
This means that the output can be used to measure any error in the frequency of the crystal unit.
Note: The 30-seconds correction could generate a carry. If such a carry occurs when the t
0
and t
1
bits are set to
(0, 1) or (1, 1), the STD.P pin output could end up low. If the ITRPT/STND bit is 0, this low-level STD.P pin
output will be held from the time that the part of the counter that is below one second is cleared by the 30-
seconds correction until the incrementation of the 1/64-second digit of the internal counter restarts. Note that
this may be different from the normal case in which the STD.P pin output is low for 7.8125 milliseconds.
The time of the low-level output of the first STD.P pin output after a RESET or STOP operation, or after 1 has
been written to the IRQ FLAG bit, may not be 7.8125 milliseconds.
If any one of the t
0
, t
1
, or ITRPT/STND bits is overwritten, the IRQ FLAG bit may become 1. Therefore, after
writing to any of these bits, it is necessary to first write 0 to the IRQ FLAG bit then wait until the IRQ FLAG bit
changes back to 1.
4. C
F
register (control register F)
(1) RESET bit (D
0
)
Writing 1 to the RESET bit clears the sub-second bits of the internal counter down to the 1/256-seconds counter. The
reset continues for as long as the RESET bit is 1. End the reset by writing 0 to the RESET bit. If the level of the CS
1
pin
goes low, the RESET bit is automatically cleared to 0.
(2) STOP bit (D
1
)
Writing 1 to the STOP bit stops the clock of the internal counter from the 1/8192 second bit onward. Writing 0 to the
STOP bit restarts the clock.
This function can be used to create a cumulative timer.
(3) 24/12 bit (D
2
)
Set the 24/12 bit to select either 12-hour clock or 24-hour clock as the timer mode. In 12-hour clock mode, the PM/AM
bit is used.
i. Switching between 12-hour clock and 24-hour clock
Writing 1 to the 24/12 bit selects 24-hour clock mode. In 24-hour clock mode, the PM/AM bit is inoperative and is
always 0. Writing 0 to the 24/12 bit selects 12-hour clock mode. In 12-hour clock mode, the PM/AM bit becomes
valid. It is 0 for a.m. times and 1 for p.m. times.
ii. Overwriting the 24/12 bit
Overwriting the contents of the 24/12 bit could destroy the contents of the registers from the H
1
register upward
(from the 1-hour digit upward). Therefore, before overwriting the 24/12 bit, it is necessary to save the contents of
the hour (H
1
, H
10
), day (D
1
, D
10
), month (MO
1
, MO
10
), year (Y
1
, Y
10
), and day-of-the-week (W) registers, then re-
write the data back into the registers to suit the new timer mode, after overwriting the 24/12 bit.
(4) TEST bit (D
3
)
The TEST bit is used by EPSON for test purposes. Operation cannot be guaranteed if 1 is written to this bit, so make
sure that it is set to 0 during power-on initialization.
Example: STD.P pin output when 1 hour is set
(Conditions: t
0
= 1, t
1
= 1, MASK = 0)
