7721 datasheet(148/577 Pages) RENESAS

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TIMER A

7721 Group User’s Manual

8–29

8.5 One-shot pulse mode

In this mode, the timer outputs a pulse which has an arbitrary width once. (Refer to “Table 8.5.1.”) Timers

A2 to A4 can be used in this mode. When a trigger occurs, the timer outputs “H” level from the TAjOUT pin

for an arbitrary time. Figure 8.5.1 shows the structures of the timer Aj mode register and timer Aj register

in the one-shot pulse mode.

Table 8.5.1 Specifications of one-shot pulse mode

Specifications

f2, f16, f64, or f512

q Countdown

q When the counter value becomes “000016,” reload register’s con-

tents are reloaded, and counting stops.

q If a trigger occurs during counting, reload register’s contents are

reloaded, and counting continues.

q When a trigger occurs. (Note)

q Internal or external trigger can be selected by software.

q When the counter value becomes “000016

,”

q When the count start bit is cleared to “0”

When counting stops.

Programmable I/O port or trigger input

One-shot pulse output

An undefined value is read out.

q While counting is stopped

When a value is written to the timer Aj register, it is written to both

of the reload register and counter.

q While counting is in progress

When a value is written to the timer Aj register, it is written only to

the reload register. (Transferred to the counter at the next reload

time.)

Item

Count source

Count operation

Output pulse width (“H”)

Count start condition

Count stop condition

Interrupt request occurrence timing

TAjIN pin’s function

TAjOUT pin’s function

Read from timer Aj register

Write to timer Aj register

[S]

n : Timer Aj register’s set value

Note: The trigger is generated with the count start bit = “1.”

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