Stopwatch Timer; Configuration Of Stopwatch Timer; Counter And Prescaler - Epson S1C63656 Technical Manual

4.9 Stopwatch Timer

4.9.1 Configuration of stopwatch timer

The S1C63656 has a 1/1,000 sec stopwatch timer. The stopwatch timer is configured of a 3-stage, 4-bit
BCD counter serving as the input clock of a 1,000 Hz signal output from the prescaler. Data can be read
out four bits (1/1,000 sec, 1/100 sec and 1/10 sec) at a time by the software.
In addition it has a direct input function that controls the stopwatch timer RUN/STOP and LAP using the
input ports K00 and K01.
Figure 4.9.1.1 is the block diagram of the stopwatch timer.
f /32
OSC1
(1,024 Hz)
[SWDIR]
K01
Direct
input
K00 control
K02–K13 [DKM2–0]
[LCURF]
The stopwatch timer can be used as a separate timer from the clock timer. In particular, digital watch
stopwatch functions can be realized easily with software.

4.9.2 Counter and prescaler

The stopwatch timer is configured of four-bit BCD counters SWD0–3, SWD4–7 and SWD8–11.
The counter SWD0–3, at the stage preceding the stopwatch timer, has a 1,000 Hz signal generated by the
prescaler for the input clock. It counts up every 1/1,000 sec, and generates 100 Hz signal. The counter
SWD4–7 has a 100 Hz signal generated by the counter SWD0–3 for the input clock. It count-up every
1/100 sec, and generated 10 Hz signal. The counter SWD8–11 has an approximated 10 Hz signal gener-
ated by the counter SWD4–7 for the input clock. It count-up every 1/10 sec, and generated 1 Hz signal.
The prescaler inputs a 1,024 Hz clock dividing f
outputs 1,000 Hz counting clock for SWD0–3. To generate a 1,000 Hz clock from 1,024 Hz, 24 pulses from
1,024 pulses that are input to the prescaler every second are taken out.
When the counter becomes the value indicated below, one pulse (1,024 Hz) that is input immediately
after to the prescaler will be pulled out.
<Counter value (msec) in which the pulse correction is performed>
39, 79, 139, 179, 219, 259, 299, 319, 359, 399, 439, 479, 539, 579, 619, 659, 699, 719, 759, 799, 839, 879, 939, 979
S1C63656 TECHNICAL MANUAL
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Stopwatch Timer)
[SWRST]
(1,000 Hz)
1,000 / 1,024 1/1,000 sec
prescaler counter
Capture
control
circuit
[SWRUN]
[EDIR]
[CRNWF]
Fig. 4.9.1.1 Block diagram of stopwatch timer
1/100 sec
counter
Capture buffer
SWD0–3 SWD4–7
reading reading
Data bus
(output from the OSC1 oscillation circuit), and
OSC1
EPSON
1/10 sec
1 Hz interrupt request
counter
10 Hz interrupt request
SWD8–11
reading
Direct RUN interrupt request
Direct LAP interrupt request
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