11-10
MSM66573 Family User's Manual
Chapter 11 PWM Function
11.4.2 PWM Operation During 16-bit Mode
During the 16-bit mode, PWM output can use the two output pins of PWM1OUT and
PWM3OUT.
The output from the PWM1OUT pin (PWM3OUT pin) goes to the High level the moment
P7_7, P8_7 is configured as a secondary function output.
PWM is started by first setting PW1RUN to "1", and then by setting PWM0RUN to "1". When
the RUN bit becomes 1, PWC begins counting, the output flip-flop is simultaneously set to
"1". PWC continues to count upward. When its value matches the contents of PWR01
(PWR23), a PWINT1 (PWINT3) interrupt request is generated, the output flip-flop is reset
to "0", and a Low level is output from the PWM1OUT pin (PWM3OUT pin). If PWC
overflows, the output flip-flop is set to "1", and the PWM1OUT pin (PWM3OUT pin) outputs
a High level. Also, the value of PWCY is loaded into PWC. Thereafter, until the RUN bit
is reset to "0", this operation will repeat and the duty controlled waveform will be output from
the PWM1OUT pin (PWM3OUT pin). When the RUN bit is reset to "0", a High level is output
to the PWMnOut pin.
However, even in the 16-bit mode, an interrupt request (PWINT2) is generated when the
value of PWC0 (lower 8 bits of PWC) matches that of PWR2 (lower 8 bits of PWR23). Also,
a PWINT0 interrupt is generated when the value of PWC0 (lower 8 bits of PWC) matches
that of PWR0 (lower 8 bits of PWR01), and an interrupt request (PWINT0) is generated
when PWC0 overflows.
[Note]
Depending upon the count clock selected for PWC, immediately after PWM is started, the
PWM output duty may be shortened (for one cycle only).
If the value of PWC is 0000H, and the value of PWR01 (PWR23) is 0000H, the duty output
is 1/65536. Increasing the value of PWR01 (PWR23) increases the output duty (High
level). If the value of PWR01 (PWR23) is FFFFH, the output is 65536/65536 or 100%
duty. To realize 0/65536 or 0% duty, use the port 1 primary function since 0% duty cannot
be realized with the PWM function.
Figure 11-4 shows an example of PWM output operation. Figure 11-5 shows an example
of the timing at which PWM output changes.