Datasheet

154
7734Q–AVR–02/12
AT90PWM81/161
Figure 13-6. PSCr0 & PSCr1 basic waveforms in One Ramp mode.
On-Time 0 = (OCRrRAH/L - OCRrSAH/L) × 1/Fclkpsc
On-Time 1 = (OCRrRBH/L - OCRrSBH/L) × 1/Fclkpsc
Dead-Time 0 = (OCRrSAH/L + 1) × 1/Fclkpsc
Dead-Time 1 = (OCRrSBH/L - OCRrRAH/L) × 1/Fclkpsc
Note: Minimal value for Dead-Time 0 = 1/Fclkpsc.
13.5.3 Fifty Percent Waveform Configuration
When PSCOUTr0 and PSCOUTr1 have the same characteristics, it’s possible to configure the
PSCR in a Fifty Percent mode. When the PSCR is in this configuration, it duplicates the
OCRrSBH/L and OCRrRBH/L registers in OCRrSAH/L and OCRrRAH/L registers. So it is not
necessary to program OCRrSAH/L and OCRrRAH/L registers.
13.6 Update of Values
The update of PSCR waveform registers are done in the following way:
• Immediately when the PSC is stopped
• At the PSC end of cycle when the PSC is running
• At the PSC end of cycle following the required condition when LOCK or AUTOLOCK modes
are used
To avoid asynchronous and incoherent values in a cycle, if an update of one of several values is
necessary, all values are updated at the same time at the end of the cycle by the PSC. The new
set of values is calculated by software and the update is initiated by software.
On-Time 0 On-Time 1
PSCOUTn0
PSCOUTn1
Dead-Time 1
Dead-Time 0
PSC Cycle
OCRnRB
OCRnSB
OCRnRA
OCRnSA
PSC Counter
0