Precautions - Epson S1C17001 Technical Manual

16.8 Precautions

• The OSC1 oscillator circuit must be set to On before operating the stopwatch timer.
• To prevent generating unnecessary interrupts, reset the SWT_IFLG register interrupt flag before permitting stop-
watch timer interrupts by the SWT_IMSK register.
• The stopwatch timer switches to Run/Stop mode when data is written to SWTRUN (D0/SWT_CTL resister) syn-
chronized with the 256 Hz signal falling edge. When 0 is written to SWTRUN, the timer switches to Stop state
after counting an additional "+1." 1 is retained for SWTRUN reading until the timer actually stops.
Figure 16.8.1 shows the Run/Stop control timing chart.
SWT_BCNT register
• Executing the slp command will destabilize a running stopwatch timer (SWTRUN = 1) during recovery from
SLEEP state. When switching to SLEEP state, set the stopwatch timer to STOP (SWTRUN = 0) before executing
the slp command.
S1C17001 TECHNICAL MANUAL
256Hz
SWTRUN(RD)
SWTRUN(WR)
27
Figure 16.8.1: Run/Stop control timing chart
EPSON
16 STOPWATCH TIMER (SWT)
28 29 30 31 32
201