Introduction
791
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Enhanced Capture (eCAP) Module
8.1
Introduction
Features for eCAP include:
•
Speed measurements of rotating machinery (for example, toothed sprockets sensed via 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 described in this guide includes the following features:
•
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
•
All above resources dedicated to a single input pin
•
When not used in capture mode, the ECAP module can be configured as a single channel PWM output
8.2
Description
The eCAP module represents one complete capture channel that can be instantiated multiple times
depending on the target device. In the context of this guide, one eCAP channel has the following
independent key resources:
•
Dedicated input capture pin
•
32-bit time base (counter)
•
4 x 32-bit time-stamp capture registers (CAP1-CAP4)
•
4-stage sequencer (Modulo4 counter) that is synchronized to external events, ECAP pin rising/falling
edges.
•
Independent edge polarity (rising/falling edge) selection for all 4 events
•
Input capture signal prescaling (from 2-62)
•
One-shot compare register (2 bits) to freeze captures after 1 to 4 time-stamp events
•
Control for continuous time-stamp captures using a 4-deep circular buffer (CAP1-CAP4) scheme
•
Interrupt capabilities on any of the 4 capture events
