ATTINY861A-SU Atmel, ATTINY861A-SU Datasheet - Page 75

• Manufacturer Part Number: ATTINY861A-SU
• Description: IC, MCU, 8BIT, 8K FLASH, 20SOIC
• Manufacturer: Atmel

Specifications of ATTINY861A-SU

• Controller Family/series: ATtiny
• No. Of I/o's: 16
• Eeprom Memory Size: 512Byte
• Ram Memory Size: 512Byte
• Cpu Speed: 20MHz
• No.: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 8KB
• Oscillator Type: External, Internal
• Rohs Compliant: Yes

11.6.1
11.6.2
11.7
Table 11-3.
11.7.1
8197B–AVR–01/10
Mode
0
1
2
3
4
Modes of Operation
Compare Match Blocking by TCNT0 Write
Using the Output Compare Unit
Normal, 8-bit Mode
ICEN0
0
0
0
1
1
Modes of operation
TCW0
0
0
1
0
1
OCF0B, but in 16-bit mode the match can set only the Output Compare Flag OCF0A as there is
only one Output Compare Unit. If the corresponding interrupt is enabled, the Output Compare
Flag generates an Output Compare interrupt. The Output Compare Flag is automatically cleared
when the interrupt is executed. Alternatively, the flag can be cleared by software by writing a log-
ical one to its I/O bit location.
Figure 11-5. Output Compare Unit, Block Diagram
All CPU write operations to the TCNT0H/L Register will block any Compare Match that occur in
the next timer clock cycle, even when the timer is stopped. This feature allows OCR0A/B to be
initialized to the same value as TCNT0 without triggering an interrupt when the Timer/Counter
clock is enabled.
Since writing TCNT0H/L will block all Compare Matches for one timer clock cycle, there are risks
involved when changing TCNT0H/L when using the Output Compare Unit, independently of
whether the Timer/Counter is running or not. If the value written to TCNT0H/L equals the
OCR0A/B value, the Compare Match will be missed.
The mode of operation, i.e., the behavior of the Timer/Counter and the Output Compare pins, is
defined by the Timer/Counter Width (TCW0), Input Capture Enable (ICEN0) and Wave Genera-
tion Mode (CTC0) bits. See
Table 11-3
In Normal 8-bit mode (see
when it passes its maximum 8-bit value (MAX = 0xFF) and then restarts from the bottom (0x00).
CTC0
X
X
X
0
1
summarises the different modes of operation.
Mode of Operation
Normal, 8-bit Mode
CTC Mode, 8-bit
Normal, 16-bit Mode
Input Capture Mode, 8-bit
Input Capture Mode, 16-bit
OCRnx
Table
“TCCR0A – Timer/Counter0 Control Register A” on page
Figure 11-5
11-3), the counter (TCNT0L) is incrementing until it overruns
=
(8/16-bit Comparator )
DATA BUS
OCFnx (Int.Req.)
shows a block diagram of the Output Compare unit.
0xFFFF
0xFFFF
OCR0A
0xFF
0xFF
TOP
Update of OCRx at
Immediate
Immediate
Immediate
Immediate
Immediate
TCNTn
TOV Flag Set on
MAX (0xFFFF)
MAX (0xFFFF)
MAX (0xFF)
MAX (0xFF)
MAX (0xFF)
82.
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