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REAL-TIME OUTPUT

7721 Group User’s Manual

10–10

10.4 Real-time output operation

When the timer Ai (i = 0, 1) count start bit is set to “1,” the counter starts counting of the count source.

The contents of pulse output data register i are output from the pulse output pins at every underflow of

Timer Ai. The timer is reloaded with the contents of the reload register and continues counting.

The timer Ai interrupt request bit is set to “1” when the counter underflows in . The interrupt request

bit retains “1” until the interrupt request is accepted or it is cleared by software.

Write the next output data into the pulse output data register i during the timer Ai interrupt routine or after

the recognition of the timer Ai interrupt request occurrence.

Figure 10.4.1 shows an example of real-time output operation.

Contents of bits 3–0 of pulse

output data register 0

RTP03 output

RTP02 output

RTP01 output

RTP00 output

Timer A0 interrupt

request bit

000316

000016

Undefined V2

00112

01102

11002

10012

00112

Undefined

Starts counting

V1 : Written by software

V2 : To avoid undefined output for these terms, follow the procedure “Processing of

avoiding undefined output before starting pulse output” in Figures 10.3.1 and 10.3.2.

V3 : Cleared to “0” when interrupt request is accepted or cleared by software.

The above figure shows an example of he following conditions:

•Pulse mode 0 selected

•RTP00–RTP03 selected

•Timer A0 register set value n = 000316

Starts pulse outputting

Undefined V2

Fig. 10.4.1 Example of real-time output operation

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