Specifications

Space Vector PWM
6-64
Space Vector PWM Waveforms
The space vector PWM waveforms generated are symmetric with respect to
the middle of each PWM period, and for this reason, it is called the symmetric
space vector PWM generation method. Figure 6–26 shows examples of the
symmetric space vector PWM waveforms.
The Unused Compare Register
Only two compare registers are used in space vector PWM output generation.
The third compare register, however, is still constantly compared with GP tim-
er 1. When a compare match happens, the corresponding compare interrupt
flag remains set and a peripheral interrupt request is generated, if the flag is
unmasked. Therefore, the compare register that is not used in the space vec-
tor PWM outputs generation can still be used to time events happening in a
specific application. Also, because of the extra delay introduced by the state
machine, the compare output transitions are delayed by one clock cycle in
space vector PWM mode.
6.7.3 Space Vector PWM Boundary Conditions
All three compare outputs become inactive when both compare registers
(CMPR1 and CMPR2) are loaded with a zero value in space vector PWM
mode. In general, it is the user’s responsibility to assure that (CMPR1) ≤
(CMPR2) ≤ (T1PR) in the space vector PWM mode. Otherwise, unpredictable
behavior may result.