ATMEGA8L ATMEL [ATMEL Corporation], ATMEGA8L Datasheet - Page 106
ATMEGA8L
Manufacturer Part Number
ATMEGA8L
Description
8-bit AVR with 8K Bytes In-System Programmable Flash
Manufacturer
ATMEL [ATMEL Corporation]
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
ATMEGA8L-6AU
Manufacturer:
ATMEL
Quantity:
675
Company:
Part Number:
ATMEGA8L-8AI
Manufacturer:
MICROCHIP
Quantity:
1 292
Company:
Part Number:
ATMEGA8L-8AU
Manufacturer:
ATMEL
Quantity:
4 590
Company:
Part Number:
ATMEGA8L-8AU
Manufacturer:
Atmel
Quantity:
7 500
Company:
Part Number:
ATMEGA8L-8AU
Manufacturer:
ATMEL
Quantity:
591
Part Number:
ATMEGA8L-8AU
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
Force Output Compare
Compare Match Blocking by
TCNT2 Write
Using the Output Compare
Unit
106
ATmega8(L)
In non-PWM Waveform Generation modes, the match output of the comparator can be
forced by writing a one to the Force Output Compare (FOC2) bit. Forcing Compare
Match will not set the OCF2 Flag or reload/clear the timer, but the OC2 pin will be
updated as if a real Compare Match had occurred (the COM21:0 bits settings define
whether the OC2 pin is set, cleared or toggled).
All CPU write operations to the TCNT2 Register will block any Compare Match that
occurs in the next timer clock cycle, even when the timer is stopped. This feature allows
OCR2 to be initialized to the same value as TCNT2 without triggering an interrupt when
the Timer/Counter clock is enabled.
Since writing TCNT2 in any mode of operation will block all compare matches for one
timer clock cycle, there are risks involved when changing TCNT2 when using the Output
Compare channel, independently of whether the Timer/Counter is running or not. If the
value written to TCNT2 equals the OCR2 value, the Compare Match will be missed,
resulting in incorrect waveform generation. Similarly, do not write the TCNT2 value
equal to BOTTOM when the counter is downcounting.
The setup of the OC2 should be performed before setting the Data Direction Register for
the port pin to output. The easiest way of setting the OC2 value is to use the Force Out-
put Compare (FOC2) strobe bit in Normal mode. The OC2 Register keeps its value even
when changing between waveform generation modes.
Be aware that the COM21:0 bits are not double buffered together with the compare
value. Changing the COM21:0 bits will take effect immediately.
2486M–AVR–12/03