Rainbow Electronics ATmega163L - Manual (Page 44)

ATmega163(L)
44
8-Bit Timer/Counter 2
Figure 37 shows the block diagram for Timer/Counter2.
Figure 37. Timer/Counter2 Block Diagram
The 8-bit Timer/Counter2 can select clock source from CK, prescaled CK, or external crystal input TOSC1. It can also be
stopped as described in the section “Timer/Counter2 Control Register - TCCR2” on page 45.
The status flags (overflow and compare match) are found in the Timer/Counter Interrupt Flag Register - TIFR. Control sig-
nals are found in the Timer/Counter Control Register TCCR2. The interrupt enable/disable settings are found in “The
Timer/Counter Interrupt Mask Register - TIMSK” on page 28.
When Timer/Counter2 is externally clocked, the external signal is synchronized with the oscillator frequency of the CPU. To
assure proper sampling of the external clock, the minimum time between two external clock transitions must be at least one
internal CPU clock period. The external clock signal is sampled on the rising edge of the internal CPU clock.
This module features a high resolution and a high accuracy usage with the lower prescaling opportunities. Similarly, the
high prescaling opportunities make this unit useful for lower speed functions or exact timing functions with infrequent
actions.
Timer/Counter2 can also be used as an 8-bit Pulse Width Modulator. In this mode, Timer/Counter2 and the output compare
register serve as a glitch-free, stand-alone PWM with centered pulses. Refer to page 48 for a detailed description on this
function.
8-BIT DATA BUS
8-BIT ASYNCH T/C2 DATA BUS
ASYNCH. STATUS
REGISTER (ASSR)
TIMER INT. FLAG
REGISTER (TIFR)
TIMER/COUNTER2
(TCNT2)
SYNCH UNIT
8-BIT COMPARATOR
OUTPUT COMPARE
REGISTER2 (OCR2)
TIMER INT. MASK
REGISTER (TIMSK)
0
0
0
7
7
7
T/C CLK SOURCE
UP/DOWN
T/C CLEAR
CONTROL
LOGIC
TOV0 TOV1
OCF1B OCF1A
ICF1 TOV2 OCF2
OCF2 TOV2 TOIE0 TOIE1 OCIE1A OCIE1B TICIE1 TOIE2 OCIE2
OCR2UB
TC2UB ICR2UB
CK
CK
PCK2
T/C2 OVER-
FLOW IRQ
T/C2 COMPARE
MATCH IRQ
T/C2 CONTROL
REGISTER (TCCR2)
CS22
COM21 PWM2
AS2
CS21
COM20
CS20 CTC2 FOC2
TOSC1
PSR2