NEC UPD703116 User Manual page 273

CHAPTER 9 TIMER/COUNTER FUNCTION
[Operation]
In PWM mode 2, TM0n performs up-count operation, and when it matches the value of CM0n3, match
interrupt INTCM0n3 is generated and TM0n is cleared (n = 0, 1).
The PWM cycle in this mode is ((BFCMn3 value + 1) × TM0n count clock). Concerning setting of data to
CM0n3, the next PWM cycle width is set to BFCMn3.
The data of BFCMn3 is automatically transferred by hardware to CM0n3 upon generation of the INTCM0n3
interrupt. Furthermore, calculation is performed by software processing started by INTCM0n3, and the data
for the next cycle is set to BFCMn3.
Data setting to CM0n0 to CM0n2, which control the PWM duty, is explained next.
Setting of data to CM0n0 to CM0n2 consists in setting the duty output from BFCMn0 to BFCMn2.
The values of BFCMn0 to BFCMn2 are automatically transferred by hardware to CM0n0 to CM0n2 upon
generation of the INTCM0n3 interrupt. Furthermore, software processing is started up and calculation
performed, and reset timing of the F/F for the next cycle is set to BFCMn0 to BFCMn2.
The PWM cycle and the PWM duty are set in the above procedure.
The F/F set/reset conditions upon match of CM0n0 to CM0n2 are as follows.
• Set:
TM0n and CM0n3 match detection and rising edge of TM0CEn bit of TMC0n register
• Reset: TM0n and CM0n0 to CM0n2 match detection
The values of DTRRn are transferred to the corresponding dead-time timers (DTMn0 to DTMn2) in
synchronization with the set/reset timing of the F/F, and down counting is started. DTMn0 to DTMn2 count
down to 000H, and stop when they count down further to FFFH.
DTMn0 to DTMn2 can automatically generate a width (dead time) at which the active levels of the positive
phase (TO0n0, TO0n2, TO0n4) and negative phase (TO0n1, TO0n3, TO0n5) do not overlap.
In this way, software processing is started by an interrupt (INTCM0n3) that occurs once during every PWM
cycle after initial setting has been performed, and by setting the PWM cycle and PWM duty to be used in the
next cycle, it is possible to automatically output a PWM waveform to TO0n0 to TO0n5 pins taking into
consideration the dead-time width (in case of interrupt culling ratio of 1/1).
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User's Manual U14492EJ5V0UD