Each block has a 16-bit PWM counter and a 16-bit prescale counter that allows a large range of PWM periods. The arrows in black indicate the external input and output pins of the PWM block while the brown arrows indicate the internal input and output signals of the PWM block. Each PWM block can generate 6 PWM outputs and has four capture channels, with channels 2 and 3 on the same external pin so that there are three external capture sources per PWM. The capture source for each channel can be selected from the external PWM capture pins and TRAP input pins together with the SYNC_IN and the TRANS_ENABLE_IN internal signals. The trap input can be used by the application to drive the PWM outputs to be held in a software-controllable state (high or low) and this event can optionally generate an interrupt. SYNC_OUT is a pulse of one clock cycle duration generated when the internal PWM counter starts or restarts. TRANS_ENABLE_OUT is a pulse synchronous with SYNC_OUT, but generated if a shadow register update occurs when the PWM counter restarts. By using the SYNDEL register, a delay can be inserted between the counter start and the generation of TRANS_ENABLE_OUT and SYNC_OUT. The PWM block has a carrier input pin that carries a special significance. Using this signal, the active phases of the PWM outputs can be further modulated which could be used to influence the speed or torque of a motor. This mode of operation is called burst mode. The carrier signal is derived from the output of Timer1. The modulating signal typically has a higher frequency than the modulated output signals.