85
7598H–AVR–07/09
ATtiny25/45/85
The Stop condition provides a Timer Enable/Disable function.
14.1.2
General Timer/Counter1 Control Register - GTCCR
• Bit 6- PWM1B: Pulse Width Modulator B Enable
When set (one) this bit enables PWM mode based on comparator OCR1B 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 - COM1B1, COM1B0: Comparator B Output Mode, Bits 1 and 0
The COM1B1 and COM1B0 control bits determine any output pin action following a compare
match with compare register B in Timer/Counter1. Output pin actions affect pin PB3 (OC1B).
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 OC1B is not connected in normal mode.
In PWM mode, these bits have different functions. Refer to
for a detailed
description.
0
1
1
1
PCK/64
CK/64
1
0
0
0
PCK/128
CK/128
1
0
0
1
PCK/256
CK/256
1
0
1
0
PCK/512
CK/512
1
0
1
1
PCK/1024
CK/1024
1
1
0
0
PCK/2048
CK/2048
1
1
0
1
PCK/4096
CK/4096
1
1
1
0
PCK/8192
CK/8192
1
1
1
1
PCK/16384
CK/16384
Table 14-2.
Timer/Counter1 Prescale Select (Continued)
CS13
CS12
CS11
CS10
Asynchronous
Clocking Mode
Synchronous
Clocking Mode
Bit
7
6
5
4
3
2
1
0
$2C ($4C)
TSM
PWM1B
COM1B1
COM1B0
FOC1B
FOC1A
PSR1
PSR0
GTCCR
Read/Write
R/W
R/W
R/W
R/W
W
W
R/W
R/W
Initial value
0
0
0
0
0
0
0
0
Table 14-3.
Comparator B Mode Select
COM1B1
COM1B0
Description
0
0
Timer/Counter Comparator B disconnected from output pin OC1B.
0
1
Toggle the OC1B output line.
1
0
Clear the OC1B output line.
1
1
Set the OC1B output line