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Table 13. SFO V5 Library Routines

Function Description

int SFO_MepDis_V5(n) Scale Factor Optimizer V5 with MEP Disabled

This routine is very similar to the SFO_MepDis() routine in the original SFO library, but with one

change. It now returns a 1 when MEP-disabled calibration is complete, or a 0 while calibration is still

running.

This function runs faster than the SFO_V5() routine and cannot be used on an ePWM channel while

HRPWM capablities are enabled for that channel. If there is a spare ePWM channel available in the

system. SFO_MepDis_V5() can be run for that channel, and the resulting MEP_ScaleFactor[n] value

can be copied into the MEP_ScaleFactor[n] for all other channels.

If SYSCLKOUT = TBCLK =100 MHz and assuming the MEP step size is 150 ps:

Typical value at 100 MHz = 66 MEP steps per unit TBCLK (10 ns)

The funtion returns a value in the variable array:

MEP_ScaleFactor[n] Number of MEP steps/SYSCLKOUT

If TBCLK is not equal to SYSCLKOUT, then the returned value must be adjusted to reflect the

correct TBCLK:

MEP steps per TBCLKK =MEP_ScaleFactor[n] * (SYSCLKOUT/TBCLK)

Example: If TBCLK = SYSCLKOUT/2,

MEP steps per TBCLK = MEP_ScaleFactor[n] * (100/50) = 66 *2 = 132

Constraints when using this function:

• SFO_MepDis_V5(n) can be used with SYSCLKOUT from 50 MHz to maximum SYSCLK

frequency. MEP diagnostics logic uses SYSCLKOUT and not TBCLK. Hence, the

SYSCLKOUT restriction is an important constraint.

• If TBCLK does not equal SYSCLKOUT, the TBCLK frequency must be great enough so that

MEP steps per TBCLK do not exceed 255. This is due to the restriction that there can be no

more than 255 MEP steps in a coarse step. For this reason it is highly recommended that

TBCLK=SYSCLKOUT.

• This function cannot be run on an ePWM channel with HRPWM capabilities enabled. Running

the SFP_MepDis_V5 function continuously in an application will generate an inaccurate

waveform on the HRPWM channel output pin.

Usage:

• If one of the ePWM modules is running in normal ePWM mode, then it can be used to run the

SFO diagnostics function. Here, the single MEP_ScaleFactor value obtained for that channel

can be copied and used as the MEP_ScaleFactor for the other ePWM modules which are

running HRPWM modules' MEP steps are similar but may not be identical.

• This routine returns a 1 when calibration is finished on the specified channel or a 0 if calibration

is still running.

• The ePWM module that is not active in HRPWM mode is still fully operational in conventional

PWM mode and used to drive PWM pins. The SFO function only makes ise of the MEP

diagnostics logic in the HRPWM circuitry.

• SFO_MepDis_V5(n) function does not require a starting Scale Factor value.

• The other ePWM modules operating in HRPWM mode incur only a 3-cycle minimum duty cycle

limitation.

int SFO_MepEn_V5(n) Scale Factor Optimizer V5 with MEP Enabled

This function runs slower that the SFO_MepDis_V5() routine and runs SFO diagnostics on an

ePWM channel with HRPWM capabilities enabled for that channel.

If SYSCLK = TBCLK = 100MHz, and assuming MEP step size is 150 ps:

Typical value at 100 MHz = 66 MEP steps per unit TBCLK (10 ns)

The function returns a value in the variable array:

MEP_ScaleFactor(n) =Number of MEP steps/SYSCLKOUT

=Number of MEP steps/TBCLK

SFO Library Software - SFO_TI_Build_V5.lib SPRU924F– April 2005– Revised October 2011

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