7721 datasheet(128/577 Pages) RENESAS

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TIMER A

7721 Group User’s Manual

8–9

8.3 Timer mode

In this mode, the timer counts an internally generated count source. (Refer to “Table 8.3.1.”) Figure 8.3.1

shows the structures of the timer Ai mode register and timer Ai register in the timer mode.

Table 8.3.1 Specifications of timer mode

(n + 1)

Item

Count source

Count operation

Division ratio

Count start condition

Count stop condition

Interrupt request occurrence timing

TAjIN pin’s function

TAjOUT pin’s function

Read from timer Ai register

Write to timer Ai register

Specifications

f2, f16, f64, or f512

• Countdown

• When a counter underflow occurs, reload register’s contents are reloaded,

and counting continues.

When the count start bit is set to “1.”

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

When a counter underflow occurs.

Programmable I/O port or gate input

Programmable I/O port or pulse output

Counter value can be read out.

q While counting is stopped

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

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

timing.)

n : Timer Ai register’s set value

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