AT90USB646-AU Datasheet, PDF (160/456 Pages) ATMEL Corporation – 8-bit Atmel Microcontroller with 64/128Kbytes of ISP Flash and USB Controller

16.8.3
• Bit 2:0 – CS22:0: Clock Select
The three Clock Select bits select the clock source to be used by the Timer/Counter, see Table
16-8.
Table 16-8.
CS22
0
0
0
0
1
1
1
1
Clock Select bit description.
CS21
CS20
Description
0
0
No clock source (Timer/Counter stopped)
0
1
clk_T2S/(no prescaling)
1
0
clk_T2S/8 (from prescaler)
1
1
clk_T2S/32 (from prescaler)
0
0
clk_T2S/64 (from prescaler)
0
1
clk_T2S/128 (from prescaler)
1
0
clk_T2S/256 (from prescaler)
1
1
clk_T2S/1024 (from prescaler)
TCNT2 – Timer/Counter Register
Bit
7
6
5
4
3
2
1
0
TCNT2[7:0]
TCNT2
Read/write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
The Timer/Counter Register gives direct access, both for read and write operations, to the
Timer/Counter unit 8-bit counter. Writing to the TCNT2 Register blocks (removes) the Compare
Match on the following timer clock. Modifying the counter (TCNT2) while the counter is running,
introduces a risk of missing a Compare Match between TCNT2 and the OCR2x Registers.
16.8.4
OCR2A – Output Compare Register A
Bit
7
6
5
4
3
2
1
0
OCR2A[7:0]
OCR2A
Read/write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
The Output Compare Register A contains an 8-bit value that is continuously compared with the
counter value (TCNT2). A match can be used to generate an Output Compare interrupt, or to
generate a waveform output on the OC2A pin.
16.8.5
OCR2B – Output Compare Register B
Bit
7
6
5
4
3
2
1
0
OCR2B[7:0]
OCR2B
Read/write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
The Output Compare Register B contains an 8-bit value that is continuously compared with the
counter value (TCNT2). A match can be used to generate an Output Compare interrupt, or to
generate a waveform output on the OC2B pin.
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