Texas Instruments 28xxx, Reference Manual

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2.1 Overview
Overview
Table 2-1 lists the seven key submodules together with a list of their main configuration parameters. For
example, if you need to adjust or control the duty cycle of a PWM waveform, then you should see the
counter-compare submodule in
Section 2.3 for relevant details.
Table 2-1. Submodule Configuration Parameters
Submodule Configuration Parameter or Option
Time-base (TB) •
Scale the time-base clock (TBCLK) relative to the system clock (SYSCLKOUT).
•
Configure the PWM time-base counter (TBCTR) frequency or period.
•
Set the mode for the time-base counter:
– count-up mode: used for asymmetric PWM
– count-down mode: used for asymmetric PWM
– count-up-and-down mode: used for symmetric PWM
•
Configure the time-base phase relative to another ePWM module.
•
Synchronize the time-base counter between modules through hardware or software.
•
Configure the direction (up or down) of the time-base counter after a synchronization event.
•
Configure how the time-base counter will behave when the device is halted by an emulator.
•
Specify the source for the synchronization output of the ePWM module:
– Synchronization input signal
– Time-base counter equal to zero
– Time-base counter equal to counter-compare B (CMPB)
– No output synchronization signal generated.
Counter-compare (CC) •
Specify the PWM duty cycle for output EPWMxA and/or output EPWMxB
•
Specify the time at which switching events occur on the EPWMxA or EPWMxB output
Action-qualifier (AQ) •
Specify the type of action taken when a time-base or counter-compare submodule event occurs:
– No action taken
– Output EPWMxA and/or EPWMxB switched high
– Output EPWMxA and/or EPWMxB switched low
– Output EPWMxA and/or EPWMxB toggled
•
Force the PWM output state through software control
•
Configure and control the PWM dead-band through software
Dead-band (DB) •
Control of traditional complementary dead-band relationship between upper and lower switches
•
Specify the output rising-edge-delay value
•
Specify the output falling-edge delay value
•
Bypass the dead-band module entirely. In this case the PWM waveform is passed through
without modification.
PWM-chopper (PC) •
Create a chopping (carrier) frequency.
•
Pulse width of the first pulse in the chopped pulse train.
•
Duty cycle of the second and subsequent pulses.
•
Bypass the PWM-chopper module entirely. In this case the PWM waveform is passed through
without modification.
Trip-zone (TZ) •
Configure the ePWM module to react to one, all, or none of the trip-zone pins.
•
Specify the tripping action taken when a fault occurs:
– Force EPWMxA and/or EPWMxB high
– Force EPWMxA and/or EPWMxB low
– Force EPWMxA and/or EPWMxB to a high-impedance state
– Configure EPWMxA and/or EPWMxB to ignore any trip condition.
•
Configure how often the ePWM will react to each trip-zone pin:
– One-shot
– Cycle-by-cycle
•
Enable the trip-zone to initiate an interrupt.
•
Bypass the trip-zone module entirely.
20 ePWM Submodules SPRU791D – November 2004 – Revised October 2007
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