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Chapter 7 16-bit Timer
16-bit High Precision PWM Output
7-7-2 Setup Example
High Precision PWM Output Setup Example (Timer 7)
The TM7IO output pin outputs the 1/4 duty PWM output waveform at 400 Hz with timer 7. Select fosc/2
(at fosc = 20 MHz) as a clock source. One cycle of the PWM output waveform is decided by the set value
of a compare register 1. "H" period of the PWM output waveform is decided by the set value of a
compare register 2.
An example setup procedure, with a description of each step is shown below.
Figure 7-7-4 Output Waveform of TM7IO Output Pin
(1) Set the TM7EN flag of the timer 7 mode
register 1 (TM7MD1) to "0" to stop timer 7
counting.
(2) Set the P1OMD4 flag of the port 1 output mode
register (P1OMD) to "1" to set the P14 pin as a
special function pin. Set the P1DIR4 flag of the
port 1 direction control register (P1DIR) to "1"
for output mode.
Add pull-up resistor, if it necessary.
(3) Set the TM7PWM flag of the timer 7 mode
register 2 (TM7MD2) to "1" to select the PWM
output.
(4) Set the TM7BCR flag of the TM7MD2 register
to "1" to select the TM7OC1 compare match
as a clear source of binary counter.
Also, set the T7PWMSL flag to "1" to select the
TM7OC2 compare match as a duty decision
source of the PWM output.
Setup Procedure
(1) Stop the counter.
TM7MD1 (x'3F78')
bp4 : TM7EN = 0
(2) Set the special function pin to output
mode.
P1OMD (x'3F2F')
bp4 :P1OMD4 = 1
P4DIR (x'3F31')
bp4 : P1DIR4 = 1
(3) Set the PWM output.
TM7MD2 (x'3F79')
bp4 : TM7PWM = 1
(4) Set the high precision PWM output
operation.
TM7MD2 (x'3F79')
bp5 : TM7BCR = 1
bp6 : T7PWMSL = 1
Description
TM7IO output
400 Hz
[ Chapter 4 I/O Ports ]