
91
AT90PWM216/316 [DATASHEET]
7710H–AVR–07/2013
Table 13-7 shows the COM0B1:0 bit functionality when the WGM02:0 bits are set to phase correct PWM mode.
Note:
1. A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case, the Compare Match is ignored,
Bits 3, 2 – Res: Reserved Bits
These bits are reserved bits in the AT90PWM216/316 and will always read as zero.
Bits 1:0 – WGM01:0: Waveform Generation Mode
Combined with the WGM02 bit found in the TCCR0B Register, these bits control the counting sequence of the
counter, the source for maximum (TOP) counter value, and what type of waveform generation to be used, see
Table 13-8. Modes of operation supported by the Timer/Counter unit are: Normal mode (counter), Clear Timer on
Compare Match (CTC) mode, and two types of Pulse Width Modulation (PWM) modes (see
“Modes of Operation”Notes:
1. MAX
= 0xFF
2. BOTTOM = 0x00
13.8.2
Timer/Counter Control Register B – TCCR0B
Table 13-7.
Compare Output Mode, Phase Correct PWM Mod
eCOM0B1
COM0B0
Description
0
Normal port operation, OC0B disconnected.
01
Reserved
10
Clear OC0B on Compare Match when up-counting. Set OC0B on
Compare Match when down-counting.
11
Set OC0B on Compare Match when up-counting. Clear OC0B on
Compare Match when down-counting.
Table 13-8.
Waveform Generation Mode Bit Description
Mode
WGM02
WGM01
WGM00
Timer/Count
er Mode of
Operation
TOP
Update of
OCRx at
TOV Flag
0
Normal
0xFF
Immediate
MAX
1
001
PWM, Phase
Correct
0xFF
TOP
BOTTOM
2
0
1
0
CTC
OCRA
Immediate
MAX
3
0
1
Fast PWM
0xFF
TOP
MAX
4
100
Reserved
–
5
101
PWM, Phase
Correct
OCRA
TOP
BOTTOM
6
110
Reserved
–
7
111
Fast PWM
OCRA
TOP
Bit
7
6
5
4
3
210
FOC0A
FOC0B
–
WGM02
CS02
CS01
CS00
TCCR0B
Read/Write
W
R
R/W
Initial Value
0