21.2 Description
The Output Compare unit 3B and Output Compare unit 4B shares the PB7 port pin for output. The outputs of the Output Compare units (OC3B and OC4B) overrides the normal PORTB7 Register when one of them is enabled (that is, when COMx[1:0] is not equal to zero). When both OC3B and OC4B are enabled at the same time, the modulator is automatically enabled.
The functional equivalent schematic of the
modulator is shown on the figure below. The schematic includes part of the Timer/Counter
units and the port B pin 7 output driver circuit. When the modulator is enabled the type of
modulation (logical AND or OR) can be selected by setting the PORTB7 Register as ‘1’.
Note: The DDRB7 controls the direction of the
port independent of the COMx[1:0] bit setting.
