ATMEGA88PV-10AU Datasheet, PDF (136/420 Pages) ATMEL Corporation – 8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash

16.11.4 TCNT1H and TCNT1L – Timer/Counter1
Bit
(0x85)
(0x84)
Read/Write
Initial Value
7
6
5
4
3
2
1
0
TCNT1[15:8]
TCNT1H
TCNT1[7:0]
TCNT1L
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
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. See Section “16.3” on
page 113.
Modifying the counter (TCNT1) while the counter is running introduces a risk of missing a com-
pare match between TCNT1 and one of the OCR1x Registers.
Writing to the TCNT1 Register blocks (removes) the compare match on the following timer clock
for all compare units.
16.11.5 OCR1AH and OCR1AL – Output Compare Register 1 A
Bit
(0x89)
(0x88)
Read/Write
Initial Value
7
6
5
4
3
2
1
0
OCR1A[15:8]
OCR1AH
OCR1A[7:0]
OCR1AL
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
16.11.6
OCR1BH and OCR1BL – Output Compare Register 1 B
Bit
(0x8B)
(0x8A)
Read/Write
Initial Value
7
6
5
4
3
2
1
0
OCR1B[15:8]
OCR1BH
OCR1B[7:0]
OCR1BL
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
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 simultaneously when the CPU writes to 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. See Section “16.3” on page 113.
136 ATmega48P/88P/168P
8025M–AVR–6/11