ATtiny5 datasheet(61/168 Pages) ATMEL

61 / 168 page

8127C–AVR–10/09

ATtiny4/5/9/10

11.7 Compare Match Output Unit

The Compare Output Mode (COM0x1:0) bits have two functions. The Waveform Generator uses

the COM0x1:0 bits for defining the Output Compare (OC0x) state at the next compare match.

Secondly the COM0x1:0 bits control the OC0x pin output source. Figure 11-7 on page 61 shows

a simplified schematic of the logic affected by the COM0x1:0 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 COM0x1:0 bits are shown. When referring to

the OC0x state, the reference is for the internal OC0x Register, not the OC0x pin. If a system

reset occur, the OC0x Register is reset to “0”.

Figure 11-7. Compare Match Output Unit, Schematic (non-PWM Mode)

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

ble on the pin. The port override function is generally independent of the Waveform Generation

mode, but there are some exceptions. See Table 11-2 on page 74, Table 11-3 on page 74 and

Table 11-4 on page 74 for details.

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. See “Register Description” on page 73

The COM0x1:0 bits have no effect on the Input Capture unit.

PORT

DDR

OCnx

Waveform

Generator

COMnx1

COMnx0

FOCnx

clk

I/O

ATtiny5 数据表(PDF) 61 Page - ATMEL Corporation