Datasheet

23. Output Compare Modulator (OCM1C2)
23.1. Overview
The Output Compare Modulator (OCM) allows generation of waveforms modulated with a carrier
frequency. The modulator uses the outputs from the Output Compare Unit C of the 16-bit Timer/Counter1
and the Output Compare Unit of the 8-bit Timer/Counter2. For more details about these Timer/Counters
see 16-bit Timer/Counter (Timer/Counter1 and Timer/Counter3) and 8-bit Timer/Counter2 with PWM.
Note that this feature is not available in ATmega103 compatibility mode.
Figure 23-1 Output Compare Modulator, Block Diagram
OC3B
Pin
OC1C /
OC2 / PB7
Timer/Counter 3
Timer/Counter 4
OC4B
When the modulator is enabled, the two output compare channels are modulated together as shown in
the block diagram above.
Related Links
16-bit Timer/Counter (Timer/Counter1 and Timer/Counter3) on page 137
8-bit Timer/Counter2 with PWM on page 215
23.2. Description
The Output Compare unit 1C and Output Compare unit 2 shares the PB7 port pin for output. The outputs
of the Output Compare units (OC1C and OC2) overrides the normal PORTB7 Register when one of them
is enabled (that is, when COMnx1:0 is not equal to zero). When both OC1C and OC2 are enabled at the
same time, the modulator is automatically enabled.
The functional equivalent schematic of the modulator is shown in the following figure. The schematic
includes part of the Timer/Counter units and the port B pin 7 output driver circuit.
Atmel ATmega64A [DATASHEET]
Atmel-8160E-ATmega64A_Datasheet_Complete-09/2015
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