Architecture
476
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Enhanced High-Resolution Pulse-Width Modulator (eHRPWM)
Each ePWM module can be configured to use or ignore the synchronization input. If the TBCTL[PHSEN]
bit is set, then the time-base counter (TBCNT) of the ePWM module will be automatically loaded with the
phase register (TBPHS) contents when one of the following conditions occur:
•
EPWMxSYNCI: Synchronization Input Pulse:
The value of the phase register is loaded into the
counter register when an input synchronization pulse is detected (TBPHS
→
TBCNT). This operation
occurs on the next valid time-base clock (TBCLK) edge.
•
Software Forced Synchronization Pulse:
Writing a 1 to the TBCTL[SWFSYNC] control bit invokes a
software forced synchronization. This pulse is ORed with the synchronization input signal, and
therefore has the same effect as a pulse on EPWMxSYNCI.
This feature enables the ePWM module to be automatically synchronized to the time base of another
ePWM module. Lead or lag phase control can be added to the waveforms generated by different ePWM
modules to synchronize them. In up-down-count mode, the TBCTL[PSHDIR] bit configures the direction of
the time-base counter immediately after a synchronization event. The new direction is independent of the
direction prior to the synchronization event. The TBPHS bit is ignored in count-up or count-down modes.
See
through
for examples.
Clearing the TBCTL[PHSEN] bit configures the ePWM to ignore the synchronization input pulse. The
synchronization pulse can still be allowed to flow-through to the EPWMxSYNCO and be used to
synchronize other ePWM modules. In this way, you can set up a master time-base (for example, ePWM1)
and downstream modules (ePWM2 - ePWMx) may elect to run in synchronization with the master.
16.2.3.4 Phase Locking the Time-Base Clocks of Multiple ePWM Modules
The TBCLKSYNC bit in the chip configuration register 1 (CFGCHIP1) in the System Module can be used
to globally synchronize the time-base clocks of all enabled ePWM modules on a device. The TBCLKSYNC
bit is part of the chip configuration registers and is described in the device-specific data manual. When
TBCLKSYNC = 0, the time-base clock of all ePWM modules is stopped (default). When TBCLKSYNC = 1,
all ePWM time-base clocks are started with the rising edge of TBCLK aligned. For perfectly synchronized
TBCLKs, the prescaler bits in the TBCTL register of each ePWM module must be set identically. The
proper procedure for enabling the ePWM clocks is as follows:
1. Enable the ePWM module clocks.
2. Set TBCLKSYNC = 0. This will stop the time-base clock within any enabled ePWM module.
3. Configure the prescaler values and desired ePWM modes.
4. Set TBCLKSYNC = 1.
16.2.3.5 Time-Base Counter Modes and Timing Waveforms
The time-base counter operates in one of four modes:
•
Up-count mode which is asymmetrical.
•
Down-count mode which is asymmetrical.
•
Up-down-count which is symmetrical.
•
Frozen where the time-base counter is held constant at the current value.
To illustrate the operation of the first three modes,
to
show when events are
generated and how the time-base responds to an EPWMxSYNCI signal.