7480 datasheet(119/337 Pages) RENESAS

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7480 Group and 7481 Group User's Manual

1-102

HARDWARE

1.13 Timer 1 and Timer 2

1.13.5 Programmable Waveform Generation Mode

(1)

Operations in Programmable Waveform Generation Mode

Operations in the programmable waveform generation mode is explained with Figure 1.13.9.

Count Sources

In the programmable waveform generation mode, timer 1 or timer 2 can select the following count

sources with the timer 1 or 2 count source selection bits:

• f(XIN)/8

• f(XIN)/64

• f(XIN)/128

• f(XIN)/256

Writes to and Reads from Timers

When ‘TL(0016 through FF16)’ is written to a timer, ‘TL’ is set in both the timer and the timer latch

( in Figure 1.13.9).

Also, the contents of the timer can be read by a read operation.

Count Operation

• When the timer 1 or 2 stop control bit is cleared to ‘0’, the timer starts counting ( in Figure 1.13.9).

• When the timer 1 or 2 stop control bit is set to ‘1’, the timer stops counting ( in Figure 1.13.9).

In the count operation, the contents of each timer are decremented by 1 at every rising edge of the

count source ( in Figure 1.13.9).

Reloading timers

When a timer reaches ‘FF16’ in the count operation, an underflow occurs at the subsequent rising

edge of the count source, and the value decremented by 1 from the contents of the timer latch is

reloaded to the timer. ( in Figure 1.13.9).

Timer interrupt

At an underflow, the timer 1 or 2 interrupt request bit is set to ‘1’; then a timer interrupt request is

generated ( in Figure 1.13.9).

Generation of Programmable Waveform

When an underflow occurs in a timer, the contents of the output level latch are output from the

following pins ( in Figure 1.13.9):

• T0 pin (Timer 1 used)

• T1 pin (Timer 2 used)

The output level of the T0 or T1 pin remains undefined until the first underflow occurs in this mode

( in Figure 1.13.9).

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