attiny25v ATMEL Corporation, attiny25v Datasheet - Page 88

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

88
ATtiny25/45/85
Figure 12-3. Timer/Counter1 Block Diagram
Three status flags (overflow and compare matches) are found in the Timer/Counter Interrupt
Flag Register - TIFR. Control signals are found in the Timer/Counter Control Registers TCCR1
and GTCCR. The interrupt enable/disable settings are found in the Timer/Counter Interrupt
Mask Register - TIMSK.
The Timer/Counter1 contains three Output Compare Registers, OCR1A, OCR1B, and OCR1C
as the data source to be compared with the Timer/Counter1 contents. In normal mode the Out-
put Compare functions are operational with all three output compare registers. OCR1A
determines action on the OC1A pin (PB1), and it can generate Timer1 OC1A interrupt in normal
mode and in PWM mode. Likewise, OCR1B determines action on the OC1B pin (PB4) and it can
generate Timer1 OC1B interrupt in normal mode and in PWM mode. OCR1C holds the
Timer/Counter maximum value, i.e. the clear on compare match value. In the normal mode an
overflow interrupt (TOV1) is generated when Timer/Counter1 counts from $FF to $00, while in
the PWM mode the overflow interrupt is generated when Timer/Counter1 counts either from $FF
to $00 or from OCR1C to $00. The inverted PWM outputs OC1A and OC1B are not connected in
normal mode.
In PWM mode, OCR1A and OCR1B provide the data values against which the Timer Counter
value is compared. Upon compare match the PWM outputs (OC1A, OC1A, OC1B, OC1B) are
generated. In PWM mode, the Timer Counter counts up to the value specified in the output com-
pare register OCR1C and starts again from $00. This feature allows limiting the counter “full”
value to a specified value, lower than $FF. Together with the many prescaler options, flexible
PWM frequency selection is provided.
8-BIT DATABUS
COMPARE REGISTER
TIMER/COUNTER1
8-BIT COMPARATOR
REGISTER (TIMSK)
TIMER/COUNTER1
TIMER INT. MASK
T/C1 OUTPUT
T/C1 OVER-
FLOW IRQ
(OCR1A)
(TCNT1)
T/C1 COMPARE
MATCH A IRQ
T/C CLEAR
REGISTER (TIFR)
TIMER INT. FLAG
T/C1 COMPARE
MATCH B IRQ
COMPARE REGISTER
8-BIT COMPARATOR
T/C1 OUTPUT
(OCR1B)
Table 12-3 on page 91
DEAD TIME GENERATOR
OC1A
(PB1)
REGISTER 1 (TCCR1)
T/C1 CONTROL
T/C CONTROL
LOGIC
OC1A
(PB0)
lists clock selection and OCR1C
COMPARE REGISTER
OC1B
(PB4)
DEAD TIME GENERATOR
8-BIT COMPARATOR
T/C1 OUTPUT
(OCR1C)
GLOBAL T/C CONTROL
REGISTER (GTCCR)
OC1B
(PB3)
2586K–AVR–01/08
CK
PCK