Epson S1C63558 4.9 Stopwatch Timer, 4.9.1 Configuration of stopwatch timer, 4.9.2 Count-uppattern

CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Stopwatch Timer)

4.9 Stopwatch Timer

4.9.1 Configuration of stopwatch timer

The S1C63558 has 1/100 sec unit and 1/10 sec unit stopwatch timer built-in. The stopwatch timer is configured with a 2 levels 4-bit BCD counter which has an input clock approximating 100 Hz signal (signal divided from OSC1 to the closest 100 Hz) and data can be read in units of 4 bits by software. Figure 4.9.1.1 shows the configuration of the stopwatch timer.

Data bus

OSC1				Stopwatch timer
		256 Hz				10 Hz
oscillation circuit	Divider		SWD0–3					SWD4–7
(fOSC1)
							10 Hz, 1 Hz
Stopwatch timer reset signal
					Interrupt				Interrupt
Stopwatch timer RUN/STOP signal					control				request

Fig. 4.9.1.1 Configuration of stopwatch timer

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 Count-up pattern

The stopwatch timer is configured of 4-bit BCD counters SWD0–SWD3 and SWD4–SWD7.

The counter SWD0–SWD3, at the stage preceding the stopwatch timer, has an approximated 100 Hz signal for the input clock. It counts up every 1/100 sec, and generates an approximated 10 Hz signal. The counter SWD4–SWD7 has an approximated 10 Hz signal generated by the counter SWD0–SWD3 for the input clock. In count-up every 1/10 sec, and generated 1 Hz signal.

Figure 4.9.2.1 shows the count-up pattern of the stopwatch timer.

SWD4–7 count-up pattern
SWD4–7 count value 0		1	2	3	4	5	6		7	8	9	0				1 Hz
Counting time (sec)	26	26		25	25	26	26		25	25	26	26
																signal
	256	256		256	256	256	256		256	256	256	256
																generation
					26	x 6 +	25		x 4 = 1 (sec)
SWD0–3 count-up pattern 1					256			256
SWD0–3 count value			0	1	2	3	4		5	6	7	8		9	0	Approximate
				3	2	3	2		3	2	3	2	3	2
Counting time (sec)																10 Hz
				256	256	256	256		256	256	256	256	256	256		signal
									25	(sec)						generation
									256
SWD0–3 count-up pattern 2
SWD0–3 count value			0	1	2	3	4		5	6	7	8		9	0	Approximate
Counting time (sec)				3	3	3	2		3	2	3	2	3	2		10 Hz
				256	256	256	256		256	256	256	256	256	256		signal
									26	(sec)						generation
									256

Fig. 4.9.2.1 Count-up pattern of stopwatch timer

S1C63558 TECHNICAL MANUAL EPSON 61