ATMEGA16-16AU SL602 Atmel, ATMEGA16-16AU SL602 Datasheet - Page 114

• Manufacturer Part Number: ATMEGA16-16AU SL602
• Manufacturer: Atmel

Timer/Counter1 –
TCNT1H and TCNT1L
Output Compare
Register 1 A –
OCR1AH and OCR1AL
Output Compare
Register 1 B –
OCR1BH and OCR1BL
Input Capture Register
1 – ICR1H and ICR1L
2466T–AVR–07/10
If external pin modes are used for the Timer/Counter1, transitions on the T1 pin will clock the
counter even if the pin is configured as an output. This feature allows software control of the
counting.
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.
Registers” on page 92.
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.
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.
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
Bit
Read/Write
Initial Value
R/W
R/W
R/W
R/W
7
0
7
0
7
0
7
0
See “Accessing 16-bit Registers” on page 92.
R/W
R/W
R/W
R/W
6
0
6
0
6
0
6
0
R/W
R/W
R/W
R/W
5
0
5
0
5
0
5
0
R/W
R/W
R/W
R/W
OCR1A[15:8]
OCR1B[15:8]
4
TCNT1[15:8]
0
4
0
4
0
4
0
OCR1A[7:0]
OCR1B[7:0]
TCNT1[7:0]
ICR1[15:8]
ICR1[7:0]
R/W
R/W
R/W
R/W
3
0
3
0
3
0
3
0
R/W
R/W
R/W
R/W
2
0
2
0
2
0
2
0
R/W
R/W
R/W
R/W
1
0
1
0
1
0
1
0
ATmega16(L)
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
See “Accessing 16-bit
OCR1AH
OCR1BH
OCR1AL
OCR1BL
TCNT1H
TCNT1L
ICR1H
ICR1L
114