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M30245 Group
2.2.10 Operation of Timer A (pulse width modulation mode, 16-bit PWM mode selected)
In pulse width modulation mode, choose functions from those listed in Table 2.2.10. Operations of the
circled items are described below. Figure 2.2.22 shows the operation timing, and Figures 2.2.23 and
2.2.24 show the set-up procedure.
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Operation
Note
Conditions: Reload register = 0003
Count source
TA
pin
iIN
input signal
Count start flag
PWM pulse output
from TA
Timer Ai interrupt
request bit
Figure 2.2.22. Operation timing of pulse width modulation mode, 16-bit PWM mode selected
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
Table 2.2.10. Choosed functions
Item
Count source
O
Internal count source (f
PWM mode
O
16-bit PWM
8-bit PWM
Count start condition
External trigger input (falling edge of input signal to the TAi
O
External trigger input (rising edge of input signal to the TAi
Timer overflow (TAj/TAk overflow)
Note: j = i – 1, but j = 4 when i = 0; k = i + 1, but k = 0 when i = 4.
(1) If the TAi
pin input level changes from "L" to "H" with the count start flag set to "1", the counter
IN
performs a down count on the count source. Also, the TAi
(2) The TAi
pin output level changes from "H" to "L" when a set time period elapses. At this
OUT
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
TAi
outputs an "L" level.
OUT
• The period of PWM pulses becomes (2
the timer Ai register is set to "0000
TAi
pin output level remains at "L".
OUT
(fi : frequency of the count source f
• Set TAi
pin's port direction register to "0".
IN
16
"H"
"L"
Set to "1" by software
"1"
(1) Start count
"0"
"H"
pin
iOUT
"L"
"1"
"0"
Note: n = 0000
to FFFE
16
page 28 of 354
/ f
/ f
/ fc
1
8
32
16
– 1)/fi, and the "H" level pulse width becomes n/fi. If
", the pulse width modulator does not work, and the the
16
, f
, f
, f
;
1
8
32
C32
, external trigger (rising edge of TAi
16
1 / f
X (2
–1)
i
Trigger is not generated by this signal
(2) Output level "H" to "L"
1 / f
X n
i
Cleared to "0" when interrupt request is
accepted, or cleared by software
16
Set-up
)
32
pin)
IN
pin)
IN
pin outputs an "H" level.
OUT
n : value of the timer)
pin input signal) is selected
IN
Cleared to "0"
by software
(3) One period is complete
(4) Stop count
2. Timer A
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