6.4.2 Edge Polarity Select and Qualifier
Functionality and features include:
• Four independent edge polarity (rising edge/falling edge) selection muxes are used, one for each capture
event.
• Each edge (up to 4) is event qualified by the Modulo4 sequencer.
• The edge event is gated to its respective CAPx register by the Mod4 counter. The CAPx register is loaded on
the falling edge.
6.4.3 Continuous/One-Shot Control
Operation of eCAP in Continuous/One-Shot mode:
• The Mod4 (2-bit) counter is incremented via edge qualified events (CEVT1-CEVT4).
• The Mod4 counter continues counting (0->1->2->3->0) and wraps around unless stopped.
• During one-shot operation, a 2-bit stop register (STOP_WRAP) is used to compare the Mod4 counter output,
and when equal, stops the Mod4 counter and inhibits further loads of the CAP1-CAP4 registers. In this mode
if TSCCTR counter is configured to reset on capture event (CEVTx) by configuring ECCTL1.CTRRSTx bit,
it will still keep resetting the TSCCTR counter on capture event (CEVTx) after the STOP_WRAP value is
reached and re-arm (REARM) has not occurred.
The continuous/one-shot block controls the start, stop and reset (zero) functions of the Mod4 counter, via a
mono-shot type of action that can be triggered by the stop-value comparator and re-armed via software control.
Once armed, the eCAP module waits for 1-4 (defined by stop-value) capture events before freezing both the
Mod4 counter and contents of CAP1-4 registers (time stamps).
Re-arming prepares the eCAP module for another capture sequence. Also, re-arming clears (to zero) the Mod4
counter and permits loading of CAP1-4 registers again, providing the CAPLDEN bit is set.
In continuous mode, the Mod4 counter continues to run (0->1->2->3->0, the one-shot action is ignored, and
capture values continue to be written to CAP1-4 in a circular buffer sequence.
CEVT1
CEVT2
CEVT3
CEVT4
One−shot
control logic
Stop
CLK
RST
Modulo 4
counter
2
Mod_eq
Stop value (2b)
ECCTL2[STOP_WRAP]
ECCTL2[RE−ARM]
ECCTL2[CONT/ONESHT]
0 1
3
2
2:4 MUX
Figure 6-7. Details of the Continuous/One-shot Block
Enhanced Capture (eCAP)
436
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
Страница 2: ......