Timer A
Mitsubishi microcomputers
M16C / 62 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
304
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
Item
Count source
PWM mode
Count start condition
Set-up
O
Internal count source (f1 / f8 / f32 / fc32)
16-bit PWM
8-bit PWM
External trigger input (falling edge of input signal to the TAiIN pin)
External trigger input (rising edge of input signal to the TAiIN pin)
Timer overflow (TB2/TAj/TAk overflow)
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
(1) If the TAiIN 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 TAiOUT pin outputs an “H” level.
(2) The TAiOUT 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
TAiOUT outputs an “L” level.
The period of PWM pulses becomes (216 – 1)/fi, and the “H” level pulse width becomes n/fi. If
the timer Ai register is set to “000016”, the pulse width modulator does not work, and the the
TAiOUT pin output level remains at “L”.
(fi : frequency of the count source f1, f8, f32, fC32;
n : value of the timer)
Operation
Note
Count source
TAiIN pin
input signal
PWM pulse output
from TAiOUT pin
Timer Ai interrupt
request bit
Count start flag
1 / fi X (2
–1)
16
Conditions: Reload register = 000316, external trigger (rising edge of TAiIN pin input signal) is selected
Trigger is not generated by this signal
“H”
“L”
“1”
“0”
Cleared to “0” when interrupt request is
accepted, or cleared by software
1 / fi X n
“1”
“0”
Set to “1” by software
(1) Start count
(2) Output level “H” to “L”
Note: n = 000016 to FFFE16
(3) One period is complete
(4) Stop count
Cleared to “0”
by software