Enhanced Capture (eCAP) Module
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15.3.2.2.5 CAP1-CAP4 Registers
These 32-bit registers are fed by the 32-bit counter timer bus, CTR[0-31] and are loaded (capture a time-
stamp) when their respective LD inputs are strobed.
Loading of the capture registers can be inhibited via control bit CAPLDEN. During one-shot operation, this
bit is cleared (loading is inhibited) automatically when a stop condition occurs, StopValue = Mod4.
CAP1 and CAP2 registers become the active period and compare registers, respectively, in APWM mode.
CAP3 and CAP4 registers become the respective shadow registers (APRD and ACMP) for CAP1 and
CAP2 during APWM operation.
15.3.2.2.6 Interrupt Control
An Interrupt can be generated on capture events (CEVT1-CEVT4, CNTOVF) or APWM events (PRDEQ,
CMPEQ). See Figure 15-107.
A counter overflow event (FFFF FFFFh->0000 0000h) is also provided as an interrupt source (CNTOVF).
The capture events are edge and sequencer qualified (that is, ordered in time) by the polarity select and
Mod4 gating, respectively.
One of these events can be selected as the interrupt source (from the eCAPn module) going to the
interrupt controller.
Seven interrupt events (CEVT1, CEVT2, CEVT3, CEVT4, CNTOVF, PRDEQ, CMPEQ) can be generated.
The interrupt enable register (ECEINT) is used to enable/disable individual interrupt event sources. The
interrupt flag register (ECFLG) indicates if any interrupt event has been latched and contains the global
interrupt flag bit (INT). An interrupt pulse is generated to the interrupt controller only if any of the interrupt
events are enabled, the flag bit is 1, and the INT flag bit is 0. The interrupt service routine must clear the
global interrupt flag bit and the serviced event via the interrupt clear register (ECCLR) before any other
interrupt pulses are generated. You can force an interrupt event via the interrupt force register (ECFRC).
This is useful for test purposes.
Note that the interrupts coming from the eCAP module are also used as DMA events. The interrupt
registers should be used to enable and clear the current DMA event in order for the eCAP module to
generate subsequent DMA events.
15.3.2.2.7 Shadow Load and Lockout Control
In capture mode, this logic inhibits (locks out) any shadow loading of CAP1 or CAP2 from APRD and
ACMP registers, respectively.
In APWM mode, shadow loading is active and two choices are permitted:
• Immediate - APRD or ACMP are transferred to CAP1 or CAP2 immediately upon writing a new value.
• On period equal, CTR[31:0] = PRD[31:0]
NOTE: The CEVT1, CEVT2, CEVT3, CEVT4 flags are only active in capture mode
(ECCTL2[CAP/APWM == 0]). The PRDEQ, CMPEQ flags are only valid in APWM mode
(ECCTL2[CAP/APWM == 1]). CNTOVF flag is valid in both modes.
1614
Pulse-Width Modulation Subsystem (PWMSS) SPRUH73H–October 2011–Revised April 2013
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