The features of the eCAP module include:
- Speed measurements of rotating machinery (for example, toothed sprockets sensed
by way of Hall sensors)
- Elapsed time measurements between position sensor pulses
- Period and duty cycle measurements of pulse train signals
- Decoding current or voltage amplitude derived from duty cycle encoded current/voltage sensors
The eCAP module features described in this chapter
include:
- 4-event time-stamp registers (each 32 bits)
- Edge polarity selection for up to four sequenced time-stamp capture events
- Interrupt on either of the four events
- Single-shot capture of up to four event time-stamps
- Continuous mode capture of time stamps in a four-deep circular buffer
- Absolute time-stamp capture
- Difference (Delta) mode time-stamp capture
- When not used in capture mode, the eCAP module can be configured as a single-channel PWM output
The capture
functionality of the Type 1 eCAP is enhanced from the Type 0 eCAP
with the following added features:
- Event
filter reset bit
- Writing a 1 to ECCTL2[CTRFILTRESET] clears the
event filter, the modulo counter, and any pending
interrupts flags. Resetting the bit is useful for
initialization and debug.
Note that this is not applicable for signal
monitoring interrupts, which do not get affected
by the event filter reset bit.
- Modulo
counter status bits
- The modulo counter (ECCTL2 [MODCNTRSTS])
indicates which capture register is loaded next.
In the Type 0 eCAP, to know the current state of
the modulo counter was not possible
- DMA trigger source
- eCAPxDMA was added as a DMA
trigger. CEVT[1-4] can be configured as the source
for eCAPxDMA.
- Input
multiplexer
- ECCTL0 [INPUTSEL] selects one of 128 input
signals, which are detailed in Section 21.3.
- EALLOW
protection
- EALLOW protection was added to critical
registers. To maintain software compatibility with Type-0,
configure DEV_CFG_REGS.ECAPTYPE to make these
registers unprotected.
The capture
functionality of the Type 2 eCAP is enhanced from the Type 1 eCAP
with the following added features:
- Added ECAPxSYNCINSEL register
- ECAPxSYNCINSEL register is
added for each eCAP to select an external SYNCIN.
Every eCAP can have a separate SYNCIN signal.
The capture functionality
of the Type 3 eCAP is enhanced from the Type 2 eCAP with the
following added features:
- Two signal monitoring units to monitor edge, pulse
width, and period
- Signal monitoring can optionally be tightly
coupled with ePWM global load strobes and trip
events
- Increased the number of multiplexed capture inputs from
128 to 256
- DMA
event generation capability in PWM mode of
operation
- ADC SOC generation capability, to trigger ADC
conversion