AT90PWM2B-16SE ATMEL [ATMEL Corporation], AT90PWM2B-16SE Datasheet - Page 98

• Manufacturer Part Number: AT90PWM2B-16SE
• Description: 8-bit Microcontroller with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

14.8.2
98
AT90PWM2/3/2B/3B
Timer/Counter Control Register B – TCCR0B
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 wave-
form generation to be used, see
unit are: Normal mode (counter), Clear Timer on Compare Match (CTC) mode, and two types of
Pulse Width Modulation (PWM) modes (see
Table 14-8.
Notes:
• Bit 7 – FOC0A: Force Output Compare A
The FOC0A bit is only active when the WGM bits specify a non-PWM mode.
However, for ensuring compatibility with future devices, this bit must be set to zero when
TCCR0B is written when operating in PWM mode. When writing a logical one to the FOC0A bit,
an immediate Compare Match is forced on the Waveform Generation unit. The OC0A output is
changed according to its COM0A1:0 bits setting. Note that the FOC0A bit is implemented as a
strobe. Therefore it is the value present in the COM0A1:0 bits that determines the effect of the
forced compare.
A FOC0A strobe will not generate any interrupt, nor will it clear the timer in CTC mode using
OCR0A as TOP.
The FOC0A bit is always read as zero.
• Bit 6 – FOC0B: Force Output Compare B
The FOC0B bit is only active when the WGM bits specify a non-PWM mode.
However, for ensuring compatibility with future devices, this bit must be set to zero when
TCCR0B is written when operating in PWM mode. When writing a logical one to the FOC0B bit,
an immediate Compare Match is forced on the Waveform Generation unit. The OC0B output is
changed according to its COM0B1:0 bits setting. Note that the FOC0B bit is implemented as a
Bit
Read/Write
Initial Value
Mode
0
1
2
3
4
5
6
7
1. MAX
2. BOTTOM = 0x00
WGM02
0
0
0
0
1
1
1
1
Waveform Generation Mode Bit Description
FOC0A
W
7
0
WGM01
= 0xFF
0
0
1
1
0
0
1
1
FOC0B
W
6
0
WGM00
Table
0
1
0
1
0
1
0
1
R
5
0
–
14-8. Modes of operation supported by the Timer/Counter
Timer/Count
er Mode of
Operation
Normal
PWM, Phase
Correct
CTC
Fast PWM
Reserved
PWM, Phase
Correct
Reserved
Fast PWM
“Modes of Operation” on page
R
4
–
0
WGM02
R
3
0
OCRA
OCRA
OCRA
0xFF
0xFF
0xFF
TOP
–
–
CS02
R
2
0
Immediate
Immediate
Update of
OCRx at
TOP
TOP
TOP
TOP
–
–
CS01
R/W
1
0
90).
Set on
TOV Flag
BOTTOM
BOTTOM
CS00
MAX
MAX
MAX
TOP
R/W
0
0
–
–
4317J–AVR–08/10
(1)(2)
TCCR0B