7906 datasheet(141/531 Pages) RENESAS

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TIMER A

7906 Group User’s Manual Rev.2.0

7-38

7.6 Pulse width modulation (PWM) mode

Timer Aj (j = 0 to 2, 4, 9) is equipped with the pulse width modulation (PWM) mode.

In this mode, the timer continuously outputs pulses which have an arbitrary width. Table 7.6.1 lists the

specifications of the PWM mode. Figure 7.6.1 shows the structures of the timer Aj register and timer Aj

mode register in the PWM mode.

Each of timers A3, A5 to A8 is not equipped with this mode.

Table 7.6.1 Specifications of PWM mode

Item

Count source fi

Count operation

PWM period/“H” level width

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

Specifications

f1, f2, f16, f64, f512, or f4096

q Countdown (operating as an 8-bit or 16-bit pulse width modulator)

q Reload register’s contents are reloaded at rising edge of PWM pulse,

and counting continues.

q A trigger generated during counting does not affect the counting.

<16-bit pulse width modulator>

<8-bit pulse width modulator>

q When a trigger is generated. (Note)

q Internal or external trigger can be selected by software.

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

At falling edge of PWM pulse

Programmable I/O port pin or trigger input pin

PWM 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.)

Period =

(216–1)

[s]

“H” level width =

[s]

Period =

(m + 1)(28–1)

“H” level width =

[s]

n(m + 1)

n : Timer Aj register’s set value

[s]

m : Timer Aj register’s low-order 8

bits’ set value

n : Timer Aj register’s high-order

8 bits’ set value

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

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