attiny25v ATMEL Corporation, attiny25v Datasheet - Page 92

• Manufacturer Part Number: attiny25v
• Description: Microcontroller With 2/4/8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

12.3
12.3.1
92
Register Description
ATtiny25/45/85
TCCR1 – Timer/Counter1 Control Register
• Bit 7- CTC1 : Clear Timer/Counter on Compare Match
When the CTC1 control bit is set (one), Timer/Counter1 is reset to $00 in the CPU clock cycle
after a compare match with OCR1C register value. If the control bit is cleared, Timer/Counter1
continues counting and is unaffected by a compare match.
• Bit 6- PWM1A: Pulse Width Modulator A Enable
When set (one) this bit enables PWM mode based on comparator OCR1A in Timer/Counter1
and the counter value is reset to $00 in the CPU clock cycle after a compare match with OCR1C
register value.
• Bits 5,4 - COM1A1, COM1A0: Comparator A Output Mode, Bits 1 and 0
The COM1A1 and COM1A0 control bits determine any output pin action following a compare
match with compare register A in Timer/Counter1. Output pin actions affect pin PB1 (OC1A).
Since this is an alternative function to an I/O port, the corresponding direction control bit must be
set (one) in order to control an output pin. Note that OC1A is not connected in normal mode.
Table 12-4.
In PWM mode, these bits have different functions. Refer to
description.
• Bits 3:0 - CS13, CS12, CS11, CS10: Clock Select Bits 3, 2, 1, and 0
The Clock Select bits 3, 2, 1, and 0 define the prescaling source of Timer/Counter1.
Table 12-5.
Bit
0x30
Read/Write
Initial value
COM1A1
CS13
0
0
1
1
0
0
0
0
0
0
CTC1
Comparator A Mode Select
Timer/Counter1 Prescale Select
R/W
COM1A0
7
0
0
1
0
1
CS12
0
0
0
0
1
1
PWM1A
R/W
6
0
Description
Timer/Counter Comparator A disconnected from output pin OC1A.
Toggle the OC1A output line.
Clear the OC1A output line.
Set the OC1A output line
COM1A1
CS11
R/W
0
0
1
1
0
0
5
0
COM1A0
R/W
4
0
CS10
0
1
0
1
0
1
CS13
R/W
3
0
Asynchronous
Clocking Mode
T/C1 stopped
PCK
PCK/2
PCK/4
PCK/8
PCK/16
Table 12-1 on page 89
CS12
R/W
2
0
CS11
R/W
1
0
Synchronous
Clocking Mode
T/C1 stopped
CK
CK/2
CK/4
CK/8
CK/16
CS10
R/W
0
0
2586K–AVR–01/08
for a detailed
TCCR1