Epson S1C63558 4.8.3 Interrupt function

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	Bit	Frequency	Clock timer timing chart
	D0	128 Hz
	D1	64 Hz
FF79H
	D2	32 Hz
	D3	16 Hz
	D0	8 Hz
	D1	4 Hz
FF7AH
	D2	2 Hz
	D3	1 Hz
32	Hz interrupt request
8	Hz interrupt request
2	Hz interrupt request
1	Hz interrupt request

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.

58 EPSON S1C63558 TECHNICAL MANUAL