Time-Base Frequency And Period - Texas Instruments Concerto F28M36 Series Technical Reference Manual

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ePWM Submodules

Time-Base Period Shadow Register

The time-base period register (TBPRD) has a shadow register. Shadowing allows the register update to

be synchronized with the hardware. The following definitions are used to describe all shadow registers in

the ePWM module:

Active Register

The active register controls the hardware and is responsible for actions that the hardware causes or

Shadow Register

The shadow register buffers or provides a temporary holding location for the active register. It has no

direct effect on any control hardware. At a strategic point in time the shadow register's content is

transferred to the active register. This prevents corruption or spurious operation due to the register

being asynchronously modified by software.

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 = 0x00) and/or a sync event as determined by the TBCTL2[PRDLDSYNC] bit. The

PRDLDSYNC bit is valid only if TBCTL[PRDLD] = 0. By default the TBPRD shadow register is

enabled. The sources for the SYNC input is explained in Time-Base Counter Synchronization section

C28 Enhanced Pulse Width Modulator (ePWM) Module

Figure 7-6. Time-Base Frequency and Period

For Up Count and Down Count

For Up and Down Count

SPRUHE8E – October 2012 – Revised November 2019

(TBPRD + 1) x T

2 x TBPRD x T

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