Specifications

Table Of Contents

I-58 EPSON S1C62740 TECHNICAL HARDWARE

CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Stopwatch Timer)

Interrupt function

The 10 Hz (approximate 10 Hz) and 1 Hz interrupts can be gener-

ated through the overflow of stopwatch timers SWL and SWH

respectively. Also, software can set whether to separately mask the

frequencies described earlier.

Figure 4.9.3 is the timing chart for the stopwatch timer.

Fig. 4.9.3

Timing chart for the

stopwatch timer

As shown in Figure 4.9.3, the interrupts are generated by the

overflow of their respective counters ("9" changing to "0"). Also, at

this time the corresponding interrupt factor flags (ISW0, ISW1) are

set to "1".

The respective interrupts can be masked separately through the

interrupt mask registers (EISW0, EISW1). However, regardless of

the setting of the interrupt mask registers, the interrupt factor flags

are set to "1" by the overflow of their corresponding counters.

Note: • Reading of interrupt factor flags is available at EI, but be careful in the

following cases.

If the interrupt mask register value corresponding to the interrupt factor

flags to be read is set to "1", an interrupt request will be generated by

the interrupt factor flags set timing, or an interrupt request will not be

generated. Be very careful when interrupt factor flags are in the same

address.

• Write the interrupt mask register only in the DI status (interrupt flag =

"0"). Writing during EI status (interrupt flag = "1") will cause malfunction.

Address

Stopwatch timer (SWL) timing chart

Stopwatch timer (SWH) timing chart

10 Hz interrupt request

1 Hz interrupt request

E8H

E7H

(1/100 sec BCD)

(1/10 sec BCD)