PRD
4
4
4
PRD
4
1
2
3
0
1
2
3
0
1
2
3
0
Z
1
2
3
4
0
1
2
3
CTR_dir
1
2
3
4
0
1
2
3
0
Up
Down
Down
Up
T
PWM =
(TBPRD + 1) x T
TBCLK
For Up Count and Down Count
For Up and Down Count
F
PWM =
1/ (T
PWM)
T
PWM =
2 x TBPRD x T
TBCLK
F
PWM =
1 / (T
PWM)
1
2
3
4
0
1
2
3
4
0
1
2
3
0
T
PWM
Z
T
PWM
T
PWM
T
PWM
ePWM Submodules
2005
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Enhanced Pulse Width Modulator (ePWM) Module
Figure 35-5. Time-Base Frequency and Period
The memory address of the shadow period register is the same as the active register. Which register is
written to or read from is determined by the TBCTL[PRDLD] bit. This bit enables and disables the TBPRD
shadow register as follows:
•
Time-Base Period Shadow Mode:
The TBPRD shadow register is enabled when TBCTL[PRDLD] = 0. Reads from and writes to the
TBPRD memory address go to the shadow register. The shadow register contents are transferred to
the active register (TBPRD (Active)
←
TBPRD (shadow)) when the time-base counter equals zero
(TBCTR = 0x0000). By default the TBPRD shadow register is enabled.
•
Time-Base Period Immediate Load Mode:
If immediate load mode is selected (TBCTL[PRDLD] = 1), then a read from or a write to the TBPRD
memory address goes directly to the active register.
35.2.2.3.2 Time-Base Clock Synchronization
Bit 1 of the device-level multiplexing control module (IOMM) register PINMMR166 is defined as the
TBCLKSYNC bit. The TBCLKSYNC bit allows users to globally synchronize all enabled ePWM modules to
the time-base clock (TBCLK). When set, all enabled ePWM module clocks are started with the first rising
edge of TBCLK aligned. For perfectly synchronized TBCLKs, the prescalers for each ePWM module must
be set identically.