ATMEGA8A-AUR Atmel, ATMEGA8A-AUR Datasheet - Page 89

• Manufacturer Part Number: ATMEGA8A-AUR
• Description: MCU AVR 8KB FLASH 16MHZ 32TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8A-AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 23
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

16.8
16.8.1
8159D–AVR–02/11
Compare Match Output Unit
Compare Output Mode and Waveform Generation
The Compare Output mode (COM1x1:0) bits have two functions. The waveform generator uses
the COM1x1:0 bits for defining the Output Compare (OC1x) state at the next Compare Match.
Secondly the COM1x1:0 bits control the OC1x pin output source.
schematic of the logic affected by the COM1x1:0 bit setting. The I/O Registers, I/O bits, and I/O
pins in the figure are shown in bold. Only the parts of the general I/O Port Control Registers
(DDR and PORT) that are affected by the COM1x1:0 bits are shown. When referring to the
OC1x state, the reference is for the internal OC1x Register, not the OC1x pin. If a System Reset
occur, the OC1x Register is reset to “0”.
Figure 16-5. Compare Match Output Unit, Schematic
The general I/O port function is overridden by the Output Compare (OC1x) from the waveform
generator if either of the COM1x1:0 bits are set. However, the OC1x pin direction (input or out-
put) is still controlled by the Data Direction Register (DDR) for the port pin. The Data Direction
Register bit for the OC1x pin (DDR_OC1x) must be set as output before the OC1x value is visi-
ble on the pin. The port override function is generally independent of the Waveform Generation
mode, but there are some exceptions. Refer to
details.
The design of the Output Compare Pin logic allows initialization of the OC1x state before the
output is enabled. Note that some COM1x1:0 bit settings are reserved for certain modes of oper-
ation.
The COM1x1:0 bits have no effect on the Input Capture unit.
The waveform generator uses the COM1x1:0 bits differently in normal, CTC, and PWM modes.
For all modes, setting the COM1x1:0 = 0 tells the waveform generator that no action on the
See “Register Description” on page 99.
COMnx1
COMnx0
FOCnx
clk
I/O
Waveform
Generator
D
D
D
PORT
DDR
OCnx
Table
Q
Q
Q
16-2,
1
0
Table 16-3
Figure 16-5
ATmega8A
OCnx
and
Pin
shows a simplified
Table 16-4
for
89