Datasheet

48
ATmega323(L)
1457E11/01
PB0(T0) will clock the counter even if the pin is configured as an output. This feature
can give the user SW control of the counting.
Timer Counter0 TCNT0
Timer/Counter2 TCNT2
These 8-bit registers contain the value of the Timer/Counters.
Both Timer/Counters is realized as up or up/down (in PWM mode) counters with read
and write access. If the Timer/Counter is written to and a clock source is selected, it con-
tinues counting in the timer clock cycle following the write operation.
Timer/Counter0 Output
Compare Register OCR0
Timer/Counter2 Output
Compare Register OCR2
The output compare registers are 8-bit read/write registers. The Timer/Counter Output
Compare Registers contains the data to be continuously compared with the
Timer/Counter. Actions on compare matches are specified in TCCR0 and TCCR2. A
software write to the Timer/Counter Register blocks compare matches in the next
Timer/Counter clock cycle. This prevents immediate interrupts when initializing the
Timer/Counter.
A compare match will set the compare interrupt flag in the CPU clock cycle following the
compare event.
Timer/Counter 0 and 2 in PWM
Mode
When PWM mode is selected, the Timer/Counter either wraps (overflows) when it
reaches $FF or it acts as an up/down counter.
If the up/down mode is selected, the Timer/Counter and the Output Compare Registers
OCR0 or OCR2 form an 8-bit, free-running, glitch-free and phase correct PWM with
outputs on the PB3(OC0/PWM0) or PD7(OC2/PWM2) pin.
If the overflow mode is selected, the Timer/Counter and the Output Compare Registers
OCR0 or OCR2 form an 8-bit, free-running and glitch-free PWM, operating with twice
the speed of the up/down counting mode.
Bit 76543210
$32 ($52) MSB LSB TCNT0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000
Bit 76543210
$24 ($44) MSB LSB TCNT2
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000
Bit 76543210
$3C ($5C) MSB LSB OCR0
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000
Bit 76543210
$23 ($43) MSB LSB OCR2
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000