204
Timer A
M
i
t
s
u
M
S
b
i
s
3
M
h
0
I
C
i
m
2
R
i
1
O
c
r
8
C
o
c
o
G
M
m
p
r
P
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t
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T
e
r
p
R
s
o
U
S
I
N
G
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E
-
C
H
I
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1
6
-
B
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C
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O
E
In pulse width modulation mode, choose functions from those listed in Table 2.2.11. Operations of the
circled items are described below. Figure 2.2.24 shows the operation timing, and Figure 2.2.25 shows the
set-up procedure.
2.2.11 Operation of Timer A (pulse width modulation mode, 16-bit PWM mode selected)
Figure 2.2.24. Operation timing of pulse width modulation mode, 16-bit PWM mode selected
Note: j = i – 1, but j = 4 when i = 0; k = i + 1, but k = 0 when i = 4.
Table 2.2.11. Choosed functions
Item
(1)
If the TAi
IN
pin input level changes from “L” to “H” with the count start flag set to “1”, the counter
performs a down count on the count source. Also, the TAi
OUT
pin outputs an “H” level.
(2) The TAi
OUT
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
TAi
OUT
outputs an “L” level.
The period of PWM pulses becomes (2
16
– 1)/fi, and the “H” level pulse width becomes n/fi. If
the timer Ai register is set to “0000
16
”, the pulse width modulator does not work, and the
TAi
OUT
pin output level remains at “L”.
(fi : frequency of the count source f
1
, f
8
, f
32
, f
C32
; n : value of the timer)
Operation
Note
Count source
PWM mode
Count start condition
Set-up
O
O
O
Internal count source (f
1
/ f
8
/ f
32
/ fc
32
)
16-bit PWM
8-bit PWM
External trigger input (falling edge of input signal to the TAi
IN
pin)
External trigger input (rising edge of input signal to the TAi
IN
pin)
Timer overflow (TB2/TAj/TAk overflow)
Count source
TA
iIN
pin
input signal
PWM pulse output
from TA
iOUT
pin
Timer Ai interrupt
request bit
Count start flag
1 / f
i
X
(2 –1)
Conditions: Reload register = 0003
16
, external trigger (rising edge of TAi
IN
pin input signal) is selected
Trigger is not generated by this signal
“H”
“H”
“L”
“L”
“1”
“0”
Cleared to “0” when interrupt request is
accepted, or cleared by software
1 / f
i
X n
“1”
“0”
Set to “1” by software
(1) Start count
(2) Output level “H” to “L”
Note: n = 0000
16
to FFFE
16
(3) One period is complete
(4) Stop count
Cleared to “0”
by software