M16CSLASH62M datasheet(349/615 Pages) RENESAS

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Timer A

Mitsubishi microcomputers

M16C / 62A Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

2-32

2.2.12 Operation of Timer A (pulse width modulation mode, 8-bit PWM mode selected)

Figure 2.2.26. Operation timing of pulse width modulation mode, with 8-bit PWM mode selected

In pulse width modulation mode, choose functions from those listed in Table 2.2.12. Operations of the

circled items are described below. Figure 2.2.26 shows the operation timing, and Figure 2.2.27 shows the

set-up procedure.

Item

Count source

PWM mode

Count start condition

Set-up

Internal count source (f1 / f8 / f32 / fc32)

16-bit PWM

8-bit PWM

External trigger input (falling edge of input signal to the TAiIN pin)

External trigger input (rising edge of input signal to the TAiIN pin)

Timer overflow (TB2/TAj/TAk overflow)

Table 2.2.12. Choosed functions

Note: j = i – 1, but j = 4 when i = 0; k = i + 1, but k = 0 when i = 4.

(1) If the TAiIN pin input level changes from “H” to “L” with the count start flag set to “1”, the counter

performs a down count on the count source. Also, the TAiOUT pin outputs an “H” level.

(2) The TAiOUT pin output level changes from “H” to “L” when a set time period elapses. At this

time, the timer Ai interrupt request bit goes to “1”.

(3) The counter reloads the content of the reload register every time PWM pulses are output for

one cycle, and continues counting.

(4) Setting the count start flag to “0” causes the counter to hold its value and to stop. Also, the

TAiOUT pin outputs an “L” level.

• The period of PWM pulses becomes (m + 1) X (28 – 1) / fi, and the “H” level pulse width

becomes n X (m + 1) / fi. If “0016” is set in the eight higher-order bits of the timer Ai register, the

pulse width modulator does not work, and the TAiOUT pin outputs “L” level, therefore the timer

Ai interrupt request is not generated.

(fi : frequency of the count source f1, f8, f32, fC32; n : value of the timer)

• When a trigger is generated, the TAiout pin outputs “L” level of same amplitude as “H” level of

the set PWM pulse, after which it starts PWM pulse output.

Operation

Note

Count source (Note 1)

Reload register high-order 8 bits = 0216

Reload register low-order 8 bits = 0216

External trigger (falling edge of TAiIN pin input signal) is selected

1 / fi X (m + 1) X (2 – 1)

TAiIN pin input

Underflow signal of 8-bit

prescaler (Note 2)

PWM pulse output from

TAiOUT pin

“H”

“L”

Timer Ai interrupt

request bit

“H”

“L”

“1”

“0”

Note 1: The 8-bit prescaler counts the count source.

Note 2: The 8-bit pulse width modulator counts the 8-bit prescaler's underflow signal.

Note 3: m = 0016 to FF16; n = 0016 to FE16.

1 / fi X (m + 1) X n

Count start flag

“1”

“0”

(1) Start count

(2) Output level “H” to “L”

Cleared to “0” when interrupt request

is accepted, or cleared by software

(3)

(4) Stop count

1 / fi X (m+1)

Conditions:

One period is

complete

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