CMPSS Module¶

The comparator subsystem (CMPSS) API provides a set of functions for programming the digital circuits of a pair of analog comparators. Functions are provided to configure each comparator and its corresponding 12-bit DAC and digital filter and to get both the latched and unlatched status of their output. There are also functions to configure the optional ramp generator circuit and to route incoming sync signals from the ePWM module.

The output signals of the CMPSS (referred to as CTRIPH, CTRIPOUTH, CTRIPL, and CTRIPOUTL) may be routed to GPIOs or other internal destinations using the X-BARs. See the X-BAR driver for details.

group cmpss_api

Defines

CMPSS_HICMP_CTL_M (CMPSS_COMPCTL_COMPHSOURCE | \ CMPSS_COMPCTL_COMPHINV | \ CMPSS_COMPCTL_ASYNCHEN)¶

CMPSS_LOCMP_CTL_M (CMPSS_COMPCTL_COMPLSOURCE | \ CMPSS_COMPCTL_COMPLINV | \ CMPSS_COMPCTL_ASYNCLEN)¶

CMPSS_INSRC_DAC 0x0000U¶: Input driven by internal DAC.

CMPSS_INSRC_PIN 0x0001U¶: Input driven by external pin.

CMPSS_INV_INVERTED 0x0002U¶: Comparator output is inverted.

CMPSS_OR_ASYNC_OUT_W_FILT 0x0040U¶: Asynch comparator output feeds into OR with latched digital filter output.

CMPSS_TRIPOUT_ASYNC_COMP 0x0000U¶: Asynchronous comparator output drives CTRIPOUT.

CMPSS_TRIPOUT_SYNC_COMP 0x0010U¶: Synchronous comparator output drives CTRIPOUT.

CMPSS_TRIPOUT_FILTER 0x0020U¶: Filter output drives CTRIPOUT.

CMPSS_TRIPOUT_LATCH 0x0030U¶: Latched filter output drives CTRIPOUT.

CMPSS_TRIP_ASYNC_COMP 0x0000U¶: Asynchronous comparator output drives CTRIP.

CMPSS_TRIP_SYNC_COMP 0x0004U¶: Synchronous comparator output drives CTRIP.

CMPSS_TRIP_FILTER 0x0008U¶: Filter output drives CTRIP.

CMPSS_TRIP_LATCH 0x000CU¶: Latched filter output drives CTRIP.

CMPSS_STS_HI_FILTOUT 0x0001U¶: High digital filter output.

CMPSS_STS_HI_LATCHFILTOUT 0x0002U¶: Latched value of high digital filter output.

CMPSS_STS_LO_FILTOUT 0x0100U¶: Low digital filter output.

CMPSS_STS_LO_LATCHFILTOUT 0x0200U¶: Latched value of low digital filter output.

CMPSS_DACVAL_SYSCLK 0x0000U¶: DAC value updated from SYSCLK.

CMPSS_DACVAL_PWMSYNC 0x0080U¶: DAC value updated from PWMSYNC.

CMPSS_DACREF_VDDA 0x0000U¶: VDDA is the voltage reference.

CMPSS_DACREF_VDAC 0x0020U¶: VDAC is the voltage reference.

CMPSS_DACSRC_SHDW 0x0000U¶: DAC value updated from shadow register.

CMPSS_DACSRC_RAMP 0x0001U¶: DAC value is updated from the ramp register.

Functions

void CMPSS_enableModule(uint32_t base)¶

Enables the CMPSS module.

This function enables the CMPSS module passed into the

base parameter.

Parameters

base: is the base address of the CMPSS module.

Return: None.

void CMPSS_disableModule(uint32_t base)¶

Disables the CMPSS module.

This function disables the CMPSS module passed into the

base parameter.

Parameters

base: is the base address of the CMPSS module.

Return: None.

void CMPSS_configHighComparator(uint32_t base, uint16_t config)¶

Sets the configuration for the high comparator.

This function configures a comparator. The

config parameter is the result of a logical OR operation between a CMPSS_INSRC_xxx value and if desired, CMPSS_INV_INVERTED and CMPSS_OR_ASYNC_OUT_W_FILT values.

Parameters

base: is the base address of the CMPSS module.
config: is the configuration of the high comparator.

The CMPSS_INSRC_xxx term can take on the following values to specify the high comparator negative input source:

CMPSS_INSRC_DAC - The internal DAC.
CMPSS_INSRC_PIN - An external pin.

CMPSS_INV_INVERTED may be ORed into config if the comparator output should be inverted.

CMPSS_OR_ASYNC_OUT_W_FILT may be ORed into config if the asynchronous comparator output should be fed into an OR gate with the latched digital filter output before it is made available for CTRIPH or CTRIPOUTH.

Return: None.

void CMPSS_configLowComparator(uint32_t base, uint16_t config)¶

Sets the configuration for the low comparator.

This function configures a comparator. The

config parameter is the result of a logical OR operation between a CMPSS_INSRC_xxx value and if desired, CMPSS_INV_INVERTED and CMPSS_OR_ASYNC_OUT_W_FILT values.

Parameters

base: is the base address of the CMPSS module.
config: is the configuration of the low comparator.

The CMPSS_INSRC_xxx term can take on the following values to specify the low comparator negative input source:

CMPSS_INSRC_DAC - The internal DAC.
CMPSS_INSRC_PIN - An external pin.

CMPSS_INV_INVERTED may be ORed into config if the comparator output should be inverted.

CMPSS_OR_ASYNC_OUT_W_FILT may be ORed into config if the asynchronous comparator output should be fed into an OR gate with the latched digital filter output before it is made available for CTRIPL or CTRIPOUTL.

Return: None.

void CMPSS_configOutputsHigh(uint32_t base, uint16_t config)¶

Sets the output signal configuration for the high comparator.

This function configures a comparator’s output signals CTRIP and CTRIPOUT. The

config parameter is the result of a logical OR operation between the CMPSS_TRIPOUT_xxx and CMPSS_TRIP_xxx values.

Parameters

base: is the base address of the CMPSS module.
config: is the configuration of the high comparator output signals.

The CMPSS_TRIPOUT_xxx term can take on the following values to specify which signal drives CTRIPOUTH:

CMPSS_TRIPOUT_ASYNC_COMP - The asynchronous comparator output.
CMPSS_TRIPOUT_SYNC_COMP - The synchronous comparator output.
CMPSS_TRIPOUT_FILTER - The output of the digital filter.
CMPSS_TRIPOUT_LATCH - The latched output of the digital filter.

The CMPSS_TRIP_xxx term can take on the following values to specify which signal drives CTRIPH:

CMPSS_TRIP_ASYNC_COMP - The asynchronous comparator output.
CMPSS_TRIP_SYNC_COMP - The synchronous comparator output.
CMPSS_TRIP_FILTER - The output of the digital filter.
CMPSS_TRIP_LATCH - The latched output of the digital filter.

Return: None.

void CMPSS_configOutputsLow(uint32_t base, uint16_t config)¶

Sets the output signal configuration for the low comparator.

This function configures a comparator’s output signals CTRIP and CTRIPOUT. The

config parameter is the result of a logical OR operation between the CMPSS_TRIPOUT_xxx and CMPSS_TRIP_xxx values.

Parameters

base: is the base address of the CMPSS module.
config: is the configuration of the low comparator output signals.

The CMPSS_TRIPOUT_xxx term can take on the following values to specify which signal drives CTRIPOUTL:

CMPSS_TRIPOUT_ASYNC_COMP - The asynchronous comparator output.
CMPSS_TRIPOUT_SYNC_COMP - The synchronous comparator output.
CMPSS_TRIPOUT_FILTER - The output of the digital filter.
CMPSS_TRIPOUT_LATCH - The latched output of the digital filter.

The CMPSS_TRIP_xxx term can take on the following values to specify which signal drives CTRIPL:

CMPSS_TRIP_ASYNC_COMP - The asynchronous comparator output.
CMPSS_TRIP_SYNC_COMP - The synchronous comparator output.
CMPSS_TRIP_FILTER - The output of the digital filter.
CMPSS_TRIP_LATCH - The latched output of the digital filter.

Return: None.

uint16_t CMPSS_getStatus(uint32_t base)¶

Gets the current comparator status.

This function returns the current status for the comparator, specifically the digital filter output and latched digital filter output.

Parameters

base: is the base address of the comparator module.

Return

Returns the current interrupt status, enumerated as a bit field of the following values:

CMPSS_STS_HI_FILTOUT - High digital filter output
CMPSS_STS_HI_LATCHFILTOUT - Latched value of high digital filter output
CMPSS_STS_LO_FILTOUT - Low digital filter output
CMPSS_STS_LO_LATCHFILTOUT - Latched value of low digital filter output

void CMPSS_configDAC(uint32_t base, uint16_t config)¶

Sets the configuration for the internal comparator DACs.

This function configures the comparator’s internal DAC. The

config parameter is the result of a logical OR operation between the CMPSS_DACVAL_xxx, CMPSS_DACREF_xxx, and CMPSS_DACSRC_xxx.

Parameters

base: is the base address of the CMPSS module.
config: is the configuration of the internal DAC.

The CMPSS_DACVAL_xxx term can take on the following values to specify when the DAC value is loaded from its shadow register:

CMPSS_DACVAL_SYSCLK - Value register updated on system clock.
CMPSS_DACVAL_PWMSYNC - Value register updated on PWM sync.

The CMPSS_DACREF_xxx term can take on the following values to specify which voltage supply is used as reference for the DACs:

CMPSS_DACREF_VDDA - VDDA is the voltage reference for the DAC.
CMPSS_DACREF_VDAC - VDAC is the voltage reference for the DAC.

The CMPSS_DACSRC_xxx term can take on the following values to specify the DAC value source for the high comparator’s internal DAC:

CMPSS_DACSRC_SHDW - The user-programmed DACVALS register.
CMPSS_DACSRC_RAMP - The ramp generator RAMPSTS register

Note: The CMPSS_DACVAL_xxx and CMPSS_DACREF_xxx terms apply to both the high and low comparators. CMPSS_DACSRC_xxx will only affect the high comparator’s internal DAC.
Return: None.

void CMPSS_setDACValueHigh(uint32_t base, uint16_t value)¶

Sets the value of the internal DAC of the high comparator.

This function sets the 12-bit value driven by the internal DAC of the high comparator. This function will load the value into the shadow register from which the actual DAC value register will be loaded. To configure which event causes this shadow load to take place, use

CMPSS_configDAC().

Parameters

base: is the base address of the comparator module.
value: is the value actively driven by the DAC.

Return: None.

void CMPSS_setDACValueLow(uint32_t base, uint16_t value)¶

Sets the value of the internal DAC of the low comparator.

This function sets the 12-bit value driven by the internal DAC of the low comparator. This function will load the value into the shadow register from which the actual DAC value register will be loaded. To configure which event causes this shadow load to take place, use

CMPSS_configDAC().

Parameters

base: is the base address of the comparator module.
value: is the value actively driven by the DAC.

Return: None.

void CMPSS_initFilterHigh(uint32_t base)¶

Initializes the digital filter of the high comparator.

This function initializes all the samples in the high comparator digital filter to the filter input value.

Parameters

base: is the base address of the comparator module.

Note: See CMPSS_configFilterHigh() for the proper initialization sequence to avoid glitches.
Return: None.

void CMPSS_initFilterLow(uint32_t base)¶

Initializes the digital filter of the low comparator.

This function initializes all the samples in the low comparator digital filter to the filter input value.

Parameters

base: is the base address of the comparator module.

Note: See CMPSS_configFilterLow() for the proper initialization sequence to avoid glitches.
Return: None.

uint16_t CMPSS_getDACValueHigh(uint32_t base)¶

Gets the value of the internal DAC of the high comparator.

This function gets the value of the internal DAC of the high comparator. The value is read from the

active registernot the shadow register to which CMPSS_setDACValueHigh() writes.

Parameters

base: is the base address of the comparator module.

Return: Returns the value driven by the internal DAC of the high comparator.

uint16_t CMPSS_getDACValueLow(uint32_t base)¶

Gets the value of the internal DAC of the low comparator.

This function gets the value of the internal DAC of the low comparator. The value is read from the

active registernot the shadow register to which CMPSS_setDACValueLow() writes.

Parameters

base: is the base address of the comparator module.

Return: Returns the value driven by the internal DAC of the low comparator.

void CMPSS_clearFilterLatchHigh(uint32_t base)¶

Causes a software reset of the high comparator digital filter output latch.

This function causes a software reset of the high comparator digital filter output latch. It will generate a single pulse of the latch reset signal.

Parameters

base: is the base address of the comparator module.

Return: None.

void CMPSS_clearFilterLatchLow(uint32_t base)¶

Causes a software reset of the low comparator digital filter output latch.

This function causes a software reset of the low comparator digital filter output latch. It will generate a single pulse of the latch reset signal.

Parameters

base: is the base address of the comparator module.

Return: None.

void CMPSS_setMaxRampValue(uint32_t base, uint16_t value)¶

Sets the ramp generator maximum reference value.

This function sets the ramp maximum reference value that will be loaded into the ramp generator.

Parameters

base: is the base address of the comparator module.
value: the ramp maximum reference value.

Return: None.

uint16_t CMPSS_getMaxRampValue(uint32_t base)¶

Gets the ramp generator maximum reference value.

Return

Returns the latched ramp maximum reference value that will be loaded into the ramp generator.

Parameters

base: is the base address of the comparator module.

void CMPSS_setRampDecValue(uint32_t base, uint16_t value)¶

Sets the ramp generator decrement value.

This function sets the value that is subtracted from the ramp value on every system clock cycle.

Parameters

base: is the base address of the comparator module.
value: is the ramp decrement value.

Return: None.

uint16_t CMPSS_getRampDecValue(uint32_t base)¶

Gets the ramp generator decrement value.

Return

Returns the latched ramp decrement value that is subtracted from the ramp value on every system clock cycle.

Parameters

base: is the base address of the comparator module.

void CMPSS_setRampDelayValue(uint32_t base, uint16_t value)¶

Sets the ramp generator delay value.

This function sets the value that configures the number of system clock cycles to delay the start of the ramp generator decrementer after a PWMSYNC event is received. Delay value can be no greater than 8191.

Parameters

base: is the base address of the comparator module.
value: is the 13-bit ramp delay value.

Return: None.

uint16_t CMPSS_getRampDelayValue(uint32_t base)¶

Gets the ramp generator delay value.

Return

Returns the latched ramp delay value that is subtracted from the ramp value on every system clock cycle.

Parameters

base: is the base address of the comparator module.

void CMPSS_setHysteresis(uint32_t base, uint16_t value)¶

Sets the comparator hysteresis settings.

This function sets the amount of hysteresis on the comparator inputs. The

value parameter indicates the amount of hysteresis desired. Passing in 0 results in none, passing in 1 results in typical hysteresis, passing in 2 results in 2x of typical hysteresis, and so on where value x of typical hysteresis is the amount configured.

Parameters

base: is the base address of the comparator module.
value: is the amount of hysteresis on the comparator inputs.

Return: None.

void CMPSS_enableLatchResetOnPWMSYNCHigh(uint32_t base)¶

Enables reset of HIGH comparator digital filter output latch on PWMSYNC

This function enables EPWMSYNCPER reset of High comparator digital filter output latch

Parameters

base: is the base address of the comparator module.

Return: None.

void CMPSS_disableLatchResetOnPWMSYNCHigh(uint32_t base)¶

Disables reset of HIGH comparator digital filter output latch on PWMSYNC

This function disables EPWMSYNCPER reset of High comparator digital filter output latch

Parameters

base: is the base address of the comparator module.

Return: None.

void CMPSS_enableLatchResetOnPWMSYNCLow(uint32_t base)¶

Enables reset of LOW comparator digital filter output latch on PWMSYNC

This function enables EPWMSYNCPER reset of Low comparator digital filter output latch

Parameters

base: is the base address of the comparator module.

Return: None.

void CMPSS_disableLatchResetOnPWMSYNCLow(uint32_t base)¶

Disables reset of LOW comparator digital filter output latch on PWMSYNC

This function disables EPWMSYNCPER reset of Low comparator digital filter output latch

Parameters

base: is the base address of the comparator module.

Return: None.

void CMPSS_configBlanking(uint32_t base, uint16_t pwmBlankSrc)¶

Sets the ePWM module blanking signal that holds trip in reset.

This function configures which PWMBLANK signal from the ePWM module will hold trip in reset when blanking is enabled.

Parameters

base: is the base address of the comparator module.
pwmBlankSrc: is the number of the PWMBLANK source.

The number of the PWMBLANK signal to be used to reset the ramp generator should be specified by passing it into the pwmBlankSrc parameter. For instance, passing a 2 into pwmBlankSrc will select PWMBLANK2.

Return: None.

void CMPSS_enableBlanking(uint32_t base)¶

Enables an ePWM blanking signal to hold trip in reset.

This function enables a selected ePWM blanking signal to hold trip in reset.

Parameters

base: is the base address of the comparator module.

Return: None.

void CMPSS_disableBlanking(uint32_t base)¶

Disables an ePWM blanking signal from holding trip in reset.

This function disables a selected ePWM blanking signal from holding trip in reset.

Parameters

base: is the base address of the comparator module.

Return: None.

void CMPSS_configFilterHigh(uint32_t base, uint16_t samplePrescale, uint16_t sampleWindow, uint16_t threshold)¶

Configures the digital filter of the high comparator.

This function configures the operation of the digital filter of the high comparator.

Parameters

base: is the base address of the comparator module.
samplePrescale: is the number of system clock cycles between samples.
sampleWindow: is the number of FIFO samples to monitor.
threshold: is the majority threshold of samples to change state.

The samplePrescale parameter specifies the number of system clock cycles between samples. It is a 10-bit value so a number higher than 1023 should not be passed as this parameter. The prescale used by digital filter is 1 more than samplePrescale value. So, the input provided should be 1 less than the expected prescale.

The sampleWindow parameter configures the size of the window of FIFO samples taken from the input that will be monitored to determine when to change the filter output. This sample window may be no larger than 32 samples.

The threshold parameter configures the threshold value to be used by the digital filter.

The filter output resolves to the majority value of the sample window where majority is defined by the value passed into the threshold parameter. For proper operation, the value of threshold must be greater than sampleWindow / 2.

To ensure proper operation of the filter, the following is the recommended function call sequence for initialization:

Configure and enable the comparator using CMPSS_configHighComparator() and CMPSS_enableModule()
Configure the digital filter using CMPSS_configFilterHigh()
Initialize the sample values using CMPSS_initFilterHigh()
Configure the module output signals CTRIP and CTRIPOUT using CMPSS_configOutputsHigh()

Return: None.

void CMPSS_configFilterLow(uint32_t base, uint16_t samplePrescale, uint16_t sampleWindow, uint16_t threshold)¶

Configures the digital filter of the low comparator.

This function configures the operation of the digital filter of the low comparator.

Parameters

base: is the base address of the comparator module.
samplePrescale: is the number of system clock cycles between samples.
sampleWindow: is the number of FIFO samples to monitor.
threshold: is the majority threshold of samples to change state.

The samplePrescale parameter specifies the number of system clock cycles between samples. It is a 10-bit value so a number higher than 1023 should not be passed as this parameter. The prescale used by digital filter is 1 more than samplePrescale value. So, the input provided should be 1 less than the expected prescale.

The sampleWindow parameter configures the size of the window of FIFO samples taken from the input that will be monitored to determine when to change the filter output. This sample window may be no larger than 32 samples.

The threshold parameter configures the threshold value to be used by the digital filter.

The filter output resolves to the majority value of the sample window where majority is defined by the value passed into the threshold parameter. For proper operation, the value of threshold must be greater than sampleWindow / 2.

To ensure proper operation of the filter, the following is the recommended function call sequence for initialization:

Configure and enable the comparator using CMPSS_configLowComparator() and CMPSS_enableModule()
Configure the digital filter using CMPSS_configFilterLow()
Initialize the sample values using CMPSS_initFilterLow()
Configure the module output signals CTRIP and CTRIPOUT using CMPSS_configOutputsLow()

Return: None.

void CMPSS_configLatchOnPWMSYNC(uint32_t base, bool highEnable, bool lowEnable)¶

Configures whether or not the digital filter latches are reset by PWMSYNC

This function configures whether or not the digital filter latches in both the high and low comparators should be reset by PWMSYNC. If the

highEnable parameter is true, the PWMSYNC will be allowed to reset the high comparator’s digital filter latch. If it is false, the ability of the PWMSYNC to reset the latch will be disabled. The lowEnable parameter has the same effect on the low comparator’s digital filter latch.

Parameters

base: is the base address of the comparator module.
highEnable: indicates filter latch settings in the high comparator.
lowEnable: indicates filter latch settings in the low comparator.

Return: None.

void CMPSS_configRamp(uint32_t base, uint16_t maxRampVal, uint16_t decrementVal, uint16_t delayVal, uint16_t pwmSyncSrc, bool useRampValShdw)¶

Configures the comparator subsystem’s ramp generator.

This function configures many of the main settings of the comparator subsystem’s ramp generator. The

maxRampVal parameter should be passed the ramp maximum reference value that will be loaded into the ramp generator. The decrementVal parameter should be passed the decrement value that will be subtracted from the ramp generator on each system clock cycle. The delayVal parameter should be passed the 13-bit number of system clock cycles the ramp generator should delay before beginning to decrement the ramp generator after a PWMSYNC signal is received.

Parameters

base: is the base address of the comparator module.
maxRampVal: is the ramp maximum reference value.
decrementVal: value is the ramp decrement value.
delayVal: is the ramp delay value.
pwmSyncSrc: is the number of the PWMSYNC source.
useRampValShdw: indicates if the max ramp shadow should be used.

These three values may be be set individually using the CMPSS_setMaxRampValue(), CMPSS_setRampDecValue(), and CMPSS_setRampDelayValue() APIs.

The number of the PWMSYNC signal to be used to reset the ramp generator should be specified by passing it into the pwmSyncSrc parameter. For instance, passing a 2 into pwmSyncSrc will select PWMSYNC2.

To indicate whether the ramp generator should reset with the value from the ramp max reference value shadow register or with the latched ramp max reference value, use the useRampValShdw parameter. Passing it true will result in the latched value being bypassed. The ramp generator will be loaded right from the shadow register. A value of false will load the ramp generator from the latched value.

Return: None.

The two comparators are referred to as the high comparator and the low comparator. Accordingly, many API functions come in pairs with both a “High” and a “Low” version. See the device’s Technical Reference Manual for diagrams showing what resources the comparators share and what they contain separately.

The code for this module is contained in driverlib/cmpss.c, with driverlib/cmpss.h containing the API declarations for use by applications.