7751 datasheet(85/540 Pages) RENESAS

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TIMER A

7751 Group User’s Manual

5–4

5.2 Block description

5.2.1 Counter and reload register (timer Ai register)

Each of timer Ai counter and reload register consists of 16 bits.

The counter down-counts each time the count source is input. In the event counter mode, it can also

function as an up-counter.

The reload register is used to store the initial value of the counter. When the counter underflows or

overflows, the reload register’s contents are reloaded into the counter.

Values are set to the counter and reload register by writing a value to the timer Ai register. Table 5.2.1

lists the memory assignment of the timer Ai register.

The value written into the timer Ai register when counting is not in progress is set to the counter and reload

reload time. The value got when reading out the timer Ai register varies according to the operating mode.

Table 5.2.2 lists reading and writing from and to the timer Ai register.

Table 5.2.2 Reading and writing from and to timer Ai register

Write

Written to only reload register.

Written to both counter and

reload register.

Operating mode

Timer mode

Event counter mode

One-shot pulse mode

Pulse width modulation (PWM) mode

Note: When reset, the contents of the timer Ai

Notes 1: Also refer to “[Precautions when operating in timer mode]” and “[Precautions when oper-

ating in event counter mode].”

2: When reading and writing to/from the timer Ai register, perform them in a unit of 16 bits.

Read

Counter value is read out.

(Note 1)

Undefined value is read out.

Table 5.2.1 Memory assignment of timer Ai register

Timer Ai register

High-order byte

Low-order byte

Timer A0 register

Address 4716

Address 4616

Timer A1 register

Address 4916

Address 4816

Timer A2 register

Address 4B16

Address 4A16

Timer A3 register

Address 4D16

Address 4C16

Timer A4 register

Address 4F16

Address 4E16

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