M16C62_M Datasheet, PDF (349/615 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

Timer A
Mitsubishi microcomputers
M16C / 62A Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
2.2.12 Operation of Timer A (pulse width modulation mode, 8-bit PWM mode selected)
In pulse width modulation mode, choose functions from those listed in Table 2.2.12. Operations of the
circled items are described below. Figure 2.2.26 shows the operation timing, and Figure 2.2.27 shows the
set-up procedure.
Table 2.2.12. Choosed functions
Item
Set-up
Count source
O Internal count source (f1 / f8 / f32 / fc32)
PWM mode
16-bit PWM
O 8-bit PWM
Count start condition O 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.
Operation (1) If the TAiIN pin input level changes from “H” to “L” 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
Note
TAiOUT pin outputs an “L” level.
• The period of PWM pulses becomes (m + 1) X (2⁸ – 1) / fi, and the “H” level pulse width
becomes n X (m + 1) / fi. If “0016” is set in the eight higher-order bits of the timer Ai register, the
pulse width modulator does not work, and the TAiOUT pin outputs “L” level, therefore the timer
Ai interrupt request is not generated.
(fi : frequency of the count source f1, f8, f32, fC32; n : value of the timer)
• When a trigger is generated, the TAiout pin outputs “L” level of same amplitude as “H” level of
the set PWM pulse, after which it starts PWM pulse output.
Conditions: Reload register high-order 8 bits = 0216
Reload register low-order 8 bits = 0216
External trigger (falling edge of TAiIN pin input signal) is selected
1 / fi X (m + 1) X (2 ⁸ – 1)
(4) Stop count
Count source (Note 1)
“1”
Count start flag
“0”
“H”
TAiIN pin input
“L”
Underflow signal of 8-bit “H”
prescaler (Note 2)
“L”
(1) Start count
(2) Output level “H” to “L”
1 / fi X (m+1)
(3) One period is
complete
PWM pulse output from “H”
TAiOUT pin
“L”
Timer Ai interrupt
“1”
request bit
“0”
1 / fi X (m + 1) X n
Cleared to “0” when interrupt request
is accepted, or cleared by software
Note 1: The 8-bit prescaler counts the count source.
Note 2: The 8-bit pulse width modulator counts the 8-bit prescaler's underflow signal.
Note 3: m = 0016 to FF16; n = 0016 to FE16.
Figure 2.2.26. Operation timing of pulse width modulation mode, with 8-bit PWM mode selected
2-32