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3 interrupt function – Epson S1C63558 User Manual

Page 68

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EPSON

S1C63558 TECHNICAL MANUAL

CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (Clock Timer)

4.8.3 Interrupt function

The clock timer can cause interrupts at the falling edge of 32 Hz, 8 Hz, 2 Hz and 1 Hz signals. Software
can set whether to mask any of these frequencies.
Figure 4.8.3.1 is the timing chart of the clock timer.

Address

FF79H

FF7AH

32 Hz interrupt request

8 Hz interrupt request

2 Hz interrupt request

1 Hz interrupt request

Bit

D0

D1

D2

D3

D0

D1

D2

D3

Frequency

Clock timer timing chart

128 Hz

64 Hz

32 Hz

16 Hz

8 Hz

4 Hz

2 Hz

1 Hz

Fig. 4.8.3.1 Timing chart of clock timer

As shown in Figure 4.8.3.1, interrupt is generated at the falling edge of the frequencies (32 Hz, 8 Hz, 2 Hz,
1 Hz). At this time, the corresponding interrupt factor flag (IT0, IT1, IT2, IT3) is set to "1". Selection of
whether to mask the separate interrupts can be made with the interrupt mask registers (EIT0, EIT1, EIT2,
EIT3). However, regardless of the interrupt mask register setting, the interrupt factor flag is set to "1" at
the falling edge of the corresponding signal.