Operation As Pwm Output (Timer 40 Only) - NEC PD789860 User Manual

9.4.4 Operation as PWM output (timer 40 only)

In the PWM output mode, a pulse of any duty ratio can be output by setting a low-level width using CR40 and a
high-level width using CRH40.
To operate timer 40 in PWM output mode, settings must be made in the following sequence.
<1> Disable operation of TM40 (TCE40 = 0).
<2> Disable timer output of TMO (TOE40 = 0).
<3> Set count values in CR40 and CRH40.
<4> Set the operation mode of timer 40 to PWM output mode (see Figure 9-5).
<5> Set the count clock for timer 40.
<6> Clear P20 to output mode (PM20 = 0) and the P20 output latch to 0 and enable timer output of TMO (TOE40
= 1).
<7> Enable the operation of TM40 (TCE40 = 1).
The operation in the PWM output mode is as follows.
<1> When the count value of TM40 matches the value set in CR40, an interrupt request signal (INTTM40) is
generated and output of timer 40 is inverted, which makes the compare register switch from CR40 to
CRH40.
<2> A match between TM40 and CR40 clears the TM40 value to 00H and then counting starts again.
<3> After that, when the count value of TM40 matches the value set in CRH40, an interrupt request signal
(INTTM40) is generated and output of timer 40 is inverted again, which makes the compare register switch
from CRH40 to CR40.
<4> A match between TM40 and CRH40 clears the TM40 value to 00H and then counting starts again.
A pulse of any duty ratio is output by repeating <1> to <4> above. Figures 9-22 and 9-23 show the operation
timing in the PWM output mode.
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CHAPTER 9 8-BIT TIMERS 30 AND 40
User's Manual U14826EJ5V0UD