![](http://datasheet.mmic.net.cn/90000/MD80C154-12-883_datasheet_2373954/MD80C154-12-883_121.png)
121
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P [DATASHEET]
8285E–AVR–02/2013
The two Timer/Counter I/O locations (TCNT1H and TCNT1L, combined TCNT1) give direct access, both for read
and for write operations, to the Timer/Counter unit 16-bit counter. To ensure that both the high and low bytes are
read and written simultaneously when the CPU accesses these registers, the access is performed using an 8-bit
temporary High Byte Register (TEMP). This temporary register is shared by all the other 16-bit registers.
SeeModifying the counter (TCNT1) while the counter is running introduces a risk of missing a compare match between
TCNT1 and one of the OCR1x Registers.
units.
16.11.5
OCR1AH and OCR1AL – Output Compare Register 1 A
16.11.6
OCR1BH and OCR1BL – Output Compare Register 1 B
The Output Compare Registers contain a 16-bit value that is continuously compared with the counter value
(TCNT1). A match can be used to generate an Output Compare interrupt, or to generate a waveform output on the
OC1x pin.
The Output Compare Registers are 16-bit in size. To ensure that both the high and low bytes are written simultane-
ously when the CPU writes to these registers, the access is performed using an 8-bit temporary High Byte Register
16.11.7
ICR1H and ICR1L – Input Capture Register 1
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 performed using an 8-bit temporary High Byte Register
Bit
765
432
10
(0x89)
OCR1A[15:8]
OCR1AH
(0x88)
OCR1A[7:0]
OCR1AL
Read/Write
R/W
Initial Value
000
00
Bit
765
432
10
(0x8B)
OCR1B[15:8]
OCR1BH
(0x8A)
OCR1B[7:0]
OCR1BL
Read/Write
R/W
Initial Value
000
00
Bit
765
432
10
(0x87)
ICR1[15:8]
ICR1H
(0x86)
ICR1[7:0]
ICR1L
Read/Write
R/W
Initial Value
000
00