ATMEGA8-16AI SL383 Atmel, ATMEGA8-16AI SL383 Datasheet - Page 87

• Manufacturer Part Number: ATMEGA8-16AI SL383
• Description: Semiconductors and Actives, Microprocessors, Microcontrollers
• Manufacturer: Atmel

Compare Match
Output Unit
2486W–AVR–02/10
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 36. 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
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.
See “16-bit Timer/Counter Register Description” on page 96.
COMnx1
COMnx0
FOCnx
clk
I/O
Waveform
Generator
Table
D
D
D
PORT
DDR
OCnx
Q
Q
Q
36,
Table 37
1
0
Figure 36
and
Table 38
ATmega8(L)
OCnx
Pin
shows a simplified
for details.
87