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M
1
6
C
2 /
9
G
o r
u
p
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
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
R
e
. v
1
1 .
2
M
r a
3 .
, 0
2
0
0
7
R
E
J
0
9
B
0
1
0
1
0 -
1
1
2
f
, f
, f
, f
, f
1
2
8
32
C32
• 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
• High level width
• Cycle time (2
• High level width n x (m+1) / fj n : set value of TAi register high-order address
8
• Cycle time
(2
• TAiS bit in the 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 undefined 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 114
f o
4
5
8
Specification
n / fj
n : set value of TAi register (i=o to 4)
16
-1) / fj fixed
fj: count source frequency (f
-1) x (m+1) / fj m : set value of TAi register low-order address
12. Timer A
, f
, f
, f
, f
)
1
2
8
32
C32
pin
IN
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