Capture Sequence For Delta Mode Time-Stamp And Rising Edge Detect - Texas Instruments Concerto F28M35 Series Technical Reference Manual

Application of the ECAP Module
8.7.3 Example 3 - Time Difference (Delta) Operation Rising Edge Trigger
This example Figure 8-25
pulse train waveforms. Here Continuous Capture mode (TSCTR counts-up without resetting, and Mod4
counter wraps around) is used. In Delta-time mode, TSCTR is Reset back to Zero on every valid event.
Here Capture events are qualified as Rising edge only. On an event, TSCTR contents (Time-Stamp) is
captured first, and then TSCTR is reset to Zero. The Mod4 counter then increments to the next state. If
TSCTR reaches FFFFFFFF (Max value), before the next event, it wraps around to 00000000 and
continues, a CNTOVF (counter overflow) Flag is set, and an Interrupt (if enabled) occurs. The advantage
of Delta-time Mode is that the CAPx contents directly give timing data without the need for CPU
calculations, that is, Period1 = T
good trigger point to read the timing data, T
Figure 8-25. Capture Sequence for Delta Mode Time-stamp and Rising Edge Detect
CEVT1
CAPx pin
FFFFFFFF
CTR[0−31]
00000000
MOD4
0
CTR
CAP1 XX
CAP2
CAP3
CAP4
814
C28 Enhanced Capture (eCAP) Module
shows how the eCAP module can be used to collect Delta timing data from
, Period2 = T
1
CEVT2
T
1
1
XX
XX
XX
Polarity selection
Capture registers [1−4]
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,...etc. As shown in the diagram, the CEVT1 event is a
2
, T , T , T are all valid here.
1 2 3 4
CEVT3
T
T
2
2
CTR value at CEVT1
All capture values valid
(can be read) at this time
SPRUH22I – April 2012 – Revised November 2019
CEVT4 CEVT1
3
T
4
3 0 1
t
4
t
1
t
2
t
3
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t