168
4317I–AVR–01/08
AT90PWM2/3/2B/3B
• Bit 7:6 – PPRE21:0 : PSC 2 Prescaler Select
This two bits select the PSC input clock division factor.All generated waveform will be modified
by this factor.
• Bit 5 – PBFM2 : Balance Flank Width Modulation
When this bit is clear, Flank Width Modulation operates on On-Time 1 only.
When this bit is set, Flank Width Modulation operates on On-Time 0 and On-Time 1.
• Bit 4 – PAOC2B : PSC 2 Asynchronous Output Control B
When this bit is set, Fault input selected to block B can act directly to PSCOUT21 and
PSCOUT23 outputs. See Section “PSC Clock Sources”, page 160.
• Bit 3 – PAOC2A : PSC 2 Asynchronous Output Control A
When this bit is set, Fault input selected to block A can act directly to PSCOUT20 and
PSCOUT22 outputs. See Section “PSC Clock Sources”, page 160.
• Bit 2 – PARUN2 : PSC 2 Autorun
When this bit is set, the PSC 2 starts with PSC1. That means that PSC 2 starts :
•
when PRUN1 bit in PCTL1 register is set,
•
or when PARUN1 bit in PCTL1 is set and PRUN0 bit in PCTL0 register is set.
• Bit 1 – PCCYC2 : PSC 2 Complete Cycle
When this bit is set, the PSC 2 completes the entire waveform cycle before halt operation
requested by clearing PRUN2. This bit is not relevant in slave mode (PARUN2 = 1).
• Bit 0 – PRUN2 : PSC 2 Run
Writing this bit to one starts the PSC 2.
When set, this bit prevails over PARUN2 bit.
16.25.14 PSC n Input A Control Register – PFRCnA
Table 16-16. PSC 2 Prescaler Selection
PPRE21
PPRE20
Description PWM2/3
Description PWM2B/3B
0
0
No divider on PSC input clock
No divider on PSC input clock
0
1
Divide the PSC input clock by 4
Divide the PSC input clock by 4
1
0
Divide the PSC input clock by 16
Divide the PSC input clock by 32
1
1
Divide the PSC clock by 64
Divide the PSC clock by 256
Bit
7
6
5
4
3
2
1
0
PCAEnA
PISELnA
PELEVnA
PFLTEnA
PRFMnA3
PRFMnA2
PRFMnA1
PRFMnA0
PFRCnA
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
