Pulse Width Modulation (Pwm) Mode - Renesas M16C/29 Series Hardware Manual

M16C/29 Group

12.1.4. Pulse Width Modulation (PWM) Mode

In PWM mode, the timer outputs pulses of a given width in succession (see Table 12.1.4.1). The counter
functions as either 16-bit pulse width modulator or 8-bit pulse width modulator. Figure 12.1.4.1 shows
TAiMR register in pulse width modulation mode. Figures 12.1.4.2 and 12.1.4.3 show examples of how a
16-bit pulse width modulator operates and how an 8-bit pulse width modulator operates.
Table 12.1.4.1. Specifications in Pulse Width Modulation Mode
Item
Count source
Count operation
16-bit PWM
8-bit PWM
Count start condition
Count stop condition
Interrupt request generation timing
TAi pin function
IN
TAi pin function
OUT
Read from timer
Write to timer
Rev.1.00 Nov 01,2004
REJ09B0101-0100Z
f , f , f , f , f
1 2 8 32 C32
• Down-count (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
• High level width
• Cycle time (2
• High level width n x (m+1) / fj n : set value of TAi register high-order address
• Cycle time (2
• TAiS bit of TABSR register is set to "1" (= start counting)
• The TAiS bit = 1 and external trigger input from the TAi
• 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
TAiS bit is set to "0" (= stop counting)
PWM pulse goes "L"
I/O port or trigger input
Pulse output
An indeterminate value is read by reading TAi register
• 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)
page 106 of 402
Specification
n / fj n : set value of TAi register (i=o to 4)
16
-1) / fj fixed fj: count source frequency (f
8
-1) x (m+1) / fj m : set value of TAi register low-order address
12.1 Timer A
, f , f , f , f )
1 2 8 32 C32
pin
IN