7733 datasheet(539/940 Pages) RENESAS

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EXTERNAL ROM VERSION

7733 Group User’s Manual

20–23

20.7 Timer A

(4) Operation in pulse output port mode

The RTP0 operation when the pulse width is not modulated and the output level reverse function is

not used is described below.

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

When the count start flag of timer A0 (A2) is set to “1,” the counter starts counting of the count

source.

When an underflow occurs, data is output from each bit of RTP0 (RTP1) according to the setting

of each bit of the pulse output data register 0 (1). This data is retained until the next underflow

occurs. Timer A0 (A2) reloads the contents of the reload register and continues counting.

When the underflow occurs in , the timer A0 (A2) interrupt request bit is set to “1.” Then, the

interrupt request bit remains set to “1” until the interrupt request is accepted or the interrupt request

bit is cleared to “0” by software.

Figure 20.7.10 shows an operation example of the pulse output port mode.

Fig. 20.7.10 Operation example of pulse output port mode

Pulse output is started.

000016

FFFF16

Timer A0 interrupt request bit

Count start flag

Undefined

n, m : Reloaded value

Counting is started.

Contents of

pulse output data register 0

3 (00112)

6 (01102)

C (11002)

9 (10012)

Contents of RTP0 output

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.

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.

RTP03 output

RTP02 output

RTP01 output

RTP00 output

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