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1745D–ATARM–04-Nov-05
AT91M55800A
19.4 Waveform Operating Mode
This mode is entered by setting the WAVE parameter in TC_CMR (Channel Mode Register).
Waveform Operating Mode allows the TC Channel to generate 1 or 2 PWM signals with the
same frequency and independently programmable duty cycles, or to generate different types
of one-shot or repetitive pulses.
In this mode, TIOA is configured as output and TIOB is defined as output if it is not used as an
external event (EEVT parameter in TC_CMR).
Figure 19-5 shows the configuration of the TC Channel when programmed in Waveform Oper-
ating Mode.
19.4.1 Compare Register A, B and C (RA, RB and RC)
In Waveform Operating Mode, RA, RB and RC are all used as compare registers.
RA Compare is used to control the TIOA output. RB Compare is used to control the TIOB (if
configured as output). RC Compare can be programmed to control TIOA and/or TIOB outputs.
RC Compare can also stop the counter clock (CPCSTOP = 1 in TC_CMR) and/or disable the
counter clock (CPCDIS = 1 in TC_CMR).
As in Capture Mode, RC Compare can also generate a trigger if CPCTRG = 1. Trigger resets
the counter so RC can control the period of PWM waveforms.
19.4.2 External Event/Trigger Conditions
An external event can be programmed to be detected on one of the clock sources (XC0, XC1,
XC2) or TIOB. The external event selected can then be used as a trigger.
The parameter EEVT in TC_CMR selects the external trigger. The parameter EEVTEDG
defines the trigger edge for each of the possible external triggers (rising, falling or both). If
EEVTEDG is cleared (none), no external event is defined.
If TIOB is defined as an external event signal (EEVT = 0), TIOB is no longer used as output
and the TC channel can only generate a waveform on TIOA.
When an external event is defined, it can be used as a trigger by setting bit ENETRG in
TC_CMR.
As in Capture Mode, the SYNC signal, the software trigger and the RC compare trigger are
also available as triggers.
19.4.3 Output Controller
The output controller defines the output level changes on TIOA and TIOB following an event.
TIOB control is used only if TIOB is defined as output (not as an external event).
The following events control TIOA and TIOB: software trigger, external event and RC com-
pare. RA compare controls TIOA and RB compare controls TIOB. Each of these events can
be programmed to set, clear or toggle the output as defined in the corresponding parameter in
TC_CMR.