Input Capture Register 1 –
ICR1H and ICR1L
Bit
7
6
5
4
3
2
1
0
ICR1[15:8]
ICR1[7:0]
ICR1H
ICR1L
Read/Write
Initial Value
R/W
0
R/W
0
R/W
0
R/W
R/W
0
R/W
0
R/W
0
R/W
0
0
The Input Capture is updated with the counter (TCNT1) value each time an event occurs
on the ICP1 pin (or optionally on the Analog Comparator Output for Timer/Counter1).
The Input Capture can be used for defining the counter TOP value.
The Input Capture Register is 16-bit in size. To ensure that both the high and Low bytes
are read simultaneously when the CPU accesses these registers, the access is per-
formed using an 8-bit temporary High byte Register (TEMP). This temporary register is
shared by all the other 16-bit registers. See “Accessing 16-bit Registers” on page 77.
Timer/Counter Interrupt Mask
Register – TIMSK(1)
Bit
7
OCIE2
R/W
0
6
TOIE2
R/W
0
5
TICIE1
R/W
0
4
OCIE1A
R/W
0
3
OCIE1B
R/W
0
2
TOIE1
R/W
0
1
–
0
TOIE0
R/W
0
TIMSK
Read/Write
Initial Value
R
0
Note:
1. This register contains interrupt control bits for several Timer/Counters, but only
Timer1 bits are described in this section. The remaining bits are described in their
respective timer sections.
• Bit 5 – TICIE1: Timer/Counter1, Input Capture Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter1 Input Capture Interrupt is enabled. The
corresponding Interrupt Vector (see “Interrupts” on page 44) is executed when the ICF1
Flag, located in TIFR, is set.
• Bit 4 – OCIE1A: Timer/Counter1, Output Compare A Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter1 Output Compare A match interrupt is enabled. The
corresponding Interrupt Vector (see “Interrupts” on page 44) is executed when the
OCF1A Flag, located in TIFR, is set.
• Bit 3 – OCIE1B: Timer/Counter1, Output Compare B Match Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter1 Output Compare B match interrupt is enabled. The
corresponding Interrupt Vector (see “Interrupts” on page 44) is executed when the
OCF1B Flag, located in TIFR, is set.
• Bit 2 – TOIE1: Timer/Counter1, Overflow Interrupt Enable
When this bit is written to one, and the I-flag in the Status Register is set (interrupts glo-
bally enabled), the Timer/Counter1 Overflow Interrupt is enabled. The corresponding
Interrupt Vector (see “Interrupts” on page 44) is executed when the TOV1 Flag, located
in TIFR, is set.
100
ATmega8(L)
2486M–AVR–12/03
ATMEL [ ATMEL ]
