attiny25v ATMEL Corporation, attiny25v Datasheet - Page 73

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

11.6.1
2586K–AVR–01/08
Compare Output Mode and Waveform Generation
Figure 11-6. Compare Match Output Unit, Schematic
The general I/O port function is overridden by the Output Compare (OC0x) from the Waveform
Generator if either of the COM0x1:0 bits are set. However, the OC0x 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 OC0x pin (DDR_OC0x) must be set as output before the OC0x value is visi-
ble on the pin. The port override function is independent of the Waveform Generation mode.
The design of the Output Compare pin logic allows initialization of the OC0x state before the out-
put is enabled. Note that some COM0x1:0 bit settings are reserved for certain modes of
operation.
The Waveform Generator uses the COM0x1:0 bits differently in Normal, CTC, and PWM modes.
For all modes, setting the COM0x1:0 = 0 tells the Waveform Generator that no action on the
OC0x Register is to be performed on the next Compare Match. For compare output actions in
the non-PWM modes refer to
page
A change of the COM0x1:0 bits state will have effect at the first Compare Match after the bits are
written. For non-PWM modes, the action can be forced to have immediate effect by using the
FOC0x strobe bits.
COMnx1
COMnx0
FOCn
clk
I/O
81, and for phase correct PWM refer to
See “Register Description” on page 80.
Waveform
Generator
Table 11-2 on page
D
D
D
PORT
DDR
OCnx
Table 11-4 on page
Q
Q
Q
80. For fast PWM mode, refer to
81.
1
0
ATtiny25/45/85
Table 11-3 on
OCn
Pin
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