7733 datasheet(540/940 Pages) RENESAS

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EXTERNAL ROM VERSION

7733 Group User’s Manual

20–24

20.7 Timer A

(5) Selectable functions

The pulse width modulation function and the RTP0 output level reverse function are described below.

q Pulse width modulation function

The RTP0 operation when the positive polarity is selected is described below.

Note: Description in ( ) is applied to the RTP1 operation.

When “the pulse width modulation selection bit by timer A1(A3)” [bit 4(5)) at address 6216] is set

to “1,” “modulated” (Refer to Figure 20.7.5.) is selected. The pulse width modulation is performed

while pins RTP00 to RTP03 (RTP10 to RTP13) output “H” level. (Refer to section “6.6 Pulse width

modulation (PWM) mode” and Figure 20.7.4.) Figure 20.7.11 shows an operation example when

“modulated” is selected.

Fig. 20.7.11 Operation example when “modulated” is selected

000016

3 (00112)

6 (01102)

C (11002)

9 (10012)

FFFF16

Timer A0 interrupt request bit

n, m : Reloaded value

RTP03 output

RTP02 output

RTP01 output

RTP00 output

Timer A1 interrupt request bit

Count start flag

Counting is started.

Contents of

pulse output data register 0

Cleared to “0” when an interrupt request is accepted;

otherwise, cleared by software.

Cleared to “0” when an interrupt request is accepted;

otherwise, cleared by software.

Pulse output is started.

Note: The output level of the pulse output port is undefined from when the pulse output port mode is set until

the first timer underflow occurs. Also, this output level is at a floating state after reset because the

pulse output port becomes the input port at that time.

In the above example, in order to shorten this undefined period, the following procedure is performed:

• A small value (n) is set to the timer counter as the initial value.

• After the first underflow occurs, the normal value (m) is set to the timer counter.

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