M16CSLASH29 datasheet(138/499 Pages) RENESAS

138 / 499 page

12. Timer A

page 114

12.1.4 Pulse Width Modulation (PWM) Mode

In PWM mode, the timer outputs pulses of a given width in succession (see Table 12.5). The counter

functions as either 16-bit pulse width modulator or 8-bit pulse width modulator. Figure 12.12 shows

TAiMR register in pulse width modulation mode. Figures 12.13 and 12.14 show examples of how a 16-

bit pulse width modulator operates and how an 8-bit pulse width modulator operates.

Table 12.5 Specifications in Pulse Width Modulation Mode

Item

Specification

Count source

f1, f2, f8, f32, fC32

Count operation

• Decrement (operating as an 8-bit or a 16-bit pulse width modulator)

• The timer reloads a new value at a rising edge of PWM pulse and continues counting

• The timer is not affected by a trigger that occurs during counting

16-bit PWM

• High level width

n / fj

n : set value of TAi register (i=o to 4)

• Cycle time (216-1) / fj fixed

fj: count source frequency (f1, f2, f8, f32, fC32)

8-bit PWM

• High level width n x (m+1) / fj n : set value of TAi register high-order address

• Cycle time (28-1) x (m+1) / fj m : set value of TAi register low-order address

Count start condition

• TAiS bit in the TABSR register is set to 1 (= start counting)

• The TAiS bit = 1 and external trigger input from the TAiIN pin

• The TAiS bit = 1 and one of the following external triggers occurs

• Timer B2 overflow or underflow,

timer Aj (j=i-1, except j=4 if i=0) overflow or underflow,

timer Ak (k=i+1, except k=0 if i=4) overflow or underflow

Count stop condition

TAiS bit is set to 0 (stop counting)

Interrupt request generation timing PWM pulse goes “L”

TAiIN pin function

I/O port or trigger input

TAiOUT pin function

Pulse output

Read from timer

An undefined value is read by reading TAi register

Write to timer

• When not counting and until the 1st count source is input after counting start

Value written to TAi register is written to both reload register and counter

• When counting (after 1st count source input)

Value written to TAi register is written to only reload register

(Transferred to counter when reloaded next)

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