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SFO Library Version Comparison

Table 13. SFO V5 Library Routines (continued)

Function Description

Constraints when using this function:

• This routine must be run on one channel at a time and cannot be run on multiple channels

concurrently. When it has finished updating the MEP_ScaleFactor for a channel, it will return a

1. If it is still calibrating, it will return a 0. A background loop should exist in the user code which

calls SFO_MepEn_V5(n) repeatedly until it returns a 1. Then the function can be called for the

next channel.

(1)

NOTE: Unlike the original SFO_MepEn(n) routine, this routine cannot

run on multiple channels concurrently.

Do not call SFO_MepEn_V5(n) for another channel until the

function returns a 1 for the current channel. Otherwise, the

MEP_ScaleFactor for both channels will become corrupted.

NOTE: SFO_MepEn_V5(n) in SFO_TI_Build_V5.lib supports only the

following HRPWM configuration:

• HRCNFG[HRLOAD] = 0 (load on CTR = ZERO)

• HRCNFG[EDGMODE] = 10(falling edge MEP control)

An upgraded version of SFO_MepEn_V5(n) in

SFO_TI_Build_V5B.lib supports all available HRPWM

configurations. When using this version, the HRCNFG register

must be initialized with the appropriate configuration after

calling SFO_MepDis_V5(n) to seed the MEP_ScaleFactor[n]

and prior to calling SFO_MepEn_V5(n).

• The SFO_MepEn_V5(n) function requires a SYSCLKOUT between 60 MHz and maximum

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

SYSCLKOUT restriction is an important constraint. It is highly recommended that

TBCLK=SYSCLKOUT.

Usage:

• After calling SFO_MepDis(n) to seed MEP_ScaleFactor[n], and prior to using the

SFO_MepEn(n) function in SPO_TI_Build_V5B.lib, the HRCNFG register must be initialized

with the desired HRPWM configuration. Otherwise, calibration will not be initiated, and calls to

SFO_MepEn_V5(n) will continuously return 0.

• The SFO_MepEn_V5(n) function requires a starting scale factor value, MEP_ScaleFactor[0].

MEP_ScaleFactor[0] needs to be initialized to a typical MEP step size value. To do this,

SFO_MepDis_V5(n) can be run on an ePWM channel while the HRPWM is disabled, and the

resulting MEP_ScaleFactor[n] value can be copied into MEP_ScaleFactor[0].

• If there are drastic environmental changes to your system (i.e., temperature/voltage), it is

generally a good idea to re-seed MEP_ScaleFactor[0] with a new typical MEP step size value

for the changed conditions.

• Because SFO_MepEn_V5(n) can be run on only one channel at a time, it is only recommended

for systems where there are no spare HRPWM channels available, so SFO calibration must be

performed on all channels with HRPWM capabilities enabled. In this case, a 6-cycle MEP

inactivity zone exists at the start of each PWM period on all HRPWM channels. See

Section 2.3.3 on duty cycle range limitations.

• The function returns:

– A one when it has finished SFO calibration for the current channel

– A zero when SFO diagnostics are still running for the channel

– A two as an error indicator after calibration has completed if the resulting

MEP_ScaleFactor for the channel differs from the original MEP_ScaleFactor[0] seed

value by more than +/- 15

The function must be called repetitively before it will return a 1. This function takes a longer time to

complete than the SFO_MepDis_V5(n) calibration.

(1)

If SFO calibration must be run on multiple channels at a time while HRPWM capabilities are enabled, the previous version of the

SFO library, SFO_TI_Build.lib, which uses more memory resources, can be used instead, and SFO_MepEn(n) can run

concurrently for up to 4 ePWM channels with HRPWM enabled.

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

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