Embedded Systems Design with the Atmel AVR Microcontroller Part II

156 CHAPTER 6. TIMING SUBSYSTEM
6.7.1.5 Input Capture Register 1 (ICR1H/ICR1L)
ICR1 is a 16-bit register used to capture the value of the TCNT1 register when a desired edge on
ICP1 pin has occurred.
6.7.1.6 Timer/Counter Interrupt Mask Register 1 (TIMSK1)
Timer 1 uses the Timer/Counter 1 Output Compare Match Interrupt Enable (OCIE1A/1B) bits,
the Timer/Counter 1 Overflow Interrupt Enable (TOIE1) bit, and the Timer/Counter 1 Input
Capture Interrupt Enable (IC1E1) bit.When the OCIE1A/B bit and the I-bit in the Status Register
are both set to one, the Timer/Counter 1 Compare Match interrupt is enabled. When the OIE1 bit
and the I-bit in the Status Register are both set to one, the Timer/Counter 1 Overflow interrupt
is enabled. When the IC1E1 bit and the I-bit in the Status Register are both set to one, the
Timer/Counter 1 Input Capture interrupt is enabled.
6.7.1.7 Timer/Counter Interrupt Flag Register (TIFR1)
Timer 1 uses the Output Compare Flag 1 A/B (OCF1A/B) which sets for an output compare
A/B match. Timer 1 also uses the Timer/Counter 1 Overflow Flag (TOV1) which sets when
Timer/Counter 1 overflows. Timer Channel 1 also uses the Timer/Counter 1 Input Capture Flag
(ICF1) which sets for an input capture event.
6.8 TIMER 2
Timer 2 is another 8-bit timer channel similar to Timer 0. The Timer 2 channel block diagram is
provided in Figure 6.13. Its registers are summarized in Figure 6.14.
6.8.0.8 Timer/Counter Control Register A and B (TCCR2A and B)
The TCCR2A and B register bits are used to:
Select the operational mode of Timer 2 using the Waveform Mode Generation (WGM2[2:0])
bits,
Determine the operation of the timer within a specific mode with the Compare Match Output
Mode (COM2A[1:0] and B) bits, and
Select the source of the Timer 2 clock using Clock Select (CS2[2:0]) bits.
The bit settings for the TCCR2A and B registers are summarized in Figure 6.15.
6.8.0.9 Timer/Counter Register(TCNT2)
The TCNT2 is the 8-bit counter for Timer 2.
6.8.0.10 Output Compare Register A and B (OCR2A and B)
The OCR2A and B registers hold a user-defined 8-bit value that is continuously compared to the
TCNT2 register.