ATMEGA8-16AI SL383 Atmel, ATMEGA8-16AI SL383 Datasheet - Page 98

• Manufacturer Part Number: ATMEGA8-16AI SL383
• Description: Semiconductors and Actives, Microprocessors, Microcontrollers
• Manufacturer: Atmel

Table 39. Waveform Generation Mode Bit Description
98
Mode
0
1
2
3
4
5
6
WGM13
ATmega8(L)
0
0
0
0
0
0
0
WGM12
(CTC1)
0
0
0
0
1
1
1
Table 38
rect or the phase and frequency correct, PWM mode.
Table 38. Compare Output Mode, Phase Correct and Phase and Frequency Correct PWM
Note:
• Bit 3 – FOC1A: Force Output Compare for channel A
• Bit 2 – FOC1B: Force Output Compare for channel B
The FOC1A/FOC1B bits are only active when the WGM13:0 bits specifies a non-PWM mode.
However, for ensuring compatibility with future devices, these bits must be set to zero when
TCCR1A is written when operating in a PWM mode. When writing a logical one to the
FOC1A/FOC1B bit, an immediate Compare Match is forced on the waveform generation unit.
The OC1A/OC1B output is changed according to its COM1x1:0 bits setting. Note that the
FOC1A/FOC1B bits are implemented as strobes. Therefore it is the value present in the
COM1x1:0 bits that determine the effect of the forced compare.
A FOC1A/FOC1B strobe will not generate any interrupt nor will it clear the timer in Clear Timer
on Compare Match (CTC) mode using OCR1A as TOP.
The FOC1A/FOC1B bits are always read as zero.
• Bit 1:0 – WGM11:0: Waveform Generation Mode
Combined with the WGM13:2 bits found in the TCCR1B 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 three types
of Pulse Width Modulation (PWM) modes.
COM1A1/
COM1B1
(PWM11)
WGM11
0
0
1
1
0
0
1
1
0
0
1
1. A special case occurs when OCR1A/OCR1B equals TOP and COM1A1/COM1B1 is set.
shows the COM1x1:0 bit functionality when the WGM13:0 bits are set to the phase cor-
“Phase Correct PWM Mode” on page 91.
(PWM10)
COM1A0/
COM1B0
WGM10
0
1
0
1
0
1
0
0
1
0
1
Timer/Counter Mode of
Operation
Normal
PWM, Phase Correct, 8-bit
PWM, Phase Correct, 9-bit
PWM, Phase Correct, 10-bit
CTC
Fast PWM, 8-bit
Fast PWM, 9-bit
Description
Normal port operation, OC1A/OC1B disconnected.
WGM13:0 = 9 or 14: Toggle OC1A on Compare Match, OC1B
disconnected (normal port operation). For all other WGM1
settings, normal port operation, OC1A/OC1B disconnected.
Clear OC1A/OC1B on Compare Match when up-counting. Set
OC1A/OC1B on Compare Match when downcounting.
Set OC1A/OC1B on Compare Match when up-counting. Clear
OC1A/OC1B on Compare Match when downcounting.
Table
(1)
39. Modes of operation supported by the Timer/Counter
(See “Modes of Operation” on page
for more details.
TOP
0xFFFF
0x00FF
0x01FF
0x03FF
OCR1A
0x00FF
0x01FF
Update of
OCR1
Immediate
TOP
TOP
TOP
Immediate
BOTTOM
BOTTOM
x
88.)
2486W–AVR–02/10
TOV1 Flag
Set on
MAX
BOTTOM
MAX
TOP
TOP
BOTTOM
BOTTOM
(1)
See