SPRUHM9H October 2014 – May 2024 TMS320F28075 , TMS320F28075-Q1 , TMS320F28076
The event-trigger submodule monitors various event conditions (shown as inputs on the left side of Figure 14-45) and can be configured to prescale these events before issuing an Interrupt request or an ADC start of conversion. The event-trigger prescaling logic can issue Interrupt requests and ADC start of conversion at:
A more detailed look at how the various register bits interact with the Interrupt and ADC start of conversion logic are shown in Figure 14-46, Figure 14-47, and Figure 14-48.
Figure 14-46 shows the event-trigger's interrupt generation logic. The interrupt-period (ETPS[INTPRD]) bits specify the number of events required to cause an interrupt pulse to be generated. The choices available are:
The selection made on ETPS[INTPSSEL] bit determines whether ETINTPS register, INTCNT2 and INTPRD2 bit fields determine frequency of events (interrupt once every 0-15 events).
The event that can cause an interrupt is configured by the interrupt selection (ETSEL[INTSEL]) and (ETSEL[INTSELCMP]) bits. The event can be one of the following:
The number of events that have occurred can be read from the interrupt event counter ETPS[INTCNT] or ETINTPS[INTCNT2] register bits based off of the selection made using ETPS[INTPSSEL]. That is, when the specified event occurs the ETPS[INTCNT] or ETINTPS[INTCNT2] bits are incremented until the bits reach the value specified by ETPS[INTPRD] or ETINTPS[INTPRD2] determined again by the selection made in ETPS[INTPSSEL]. When ETPS[INTCNT] = ETPS[INTPRD], the counter stops counting and the counter output is set. The counter is only cleared when an interrupt is sent to the interrupt controller.
When ETPS[INTCNT] reaches ETPS[INTPRD], the following behavior occurs. [The following behavior is also applicable to ETINTPS[INTCNT2] and ETINTPS[INTPRD2]:
Writing a 0 to the INTPRD bits automatically clears the counter (INTCNT = 0) and the counter output resets (so no interrupts are generated). For all other writes to INTPRD, INTCNT retains the previous value. INTCNT resets when INTCNT overflows. Writing a 1 to the ETFRC[INT] bit increments the event counter INTCNT. The counter behaves as previously described when INTCNT = INTPRD. When INTPRD = 0, the counter is disabled and hence no events are detected and the ETFRC[INT] bit is also ignored. The same applies to ETINTPS[INTCNT2] and ETINTPS[INTPRD2].
The previous definition means that an interrupt on every event, on every second event, or on every third event if using the INTCNT and INTPRD can be generated. An interrupt on every event up to 15 events if using the INTCNT2 and INTPRD2 can be generated.
The INTCNT2 value can be initialized with the value from ETCNTINIT[INTINIT] based on the selection made in ETCNTINITCTL[INTINITEN]. When ETCNTINITCTL[INTINITEN] is set, then initialization of INTCNT2 counter with contents of ETCNTINIT[INTINIT] on a SYNC event or software force is determined by ETCNTINITCTL[INTINITFRC].
Figure 14-47 shows the operation of the event-trigger's start-of-conversion-A (SOCA) pulse generator. The enhancements include SOCASELCMP and SOCBSELCMP bit fields defined in the ETSEL register enable CMPC and CMPD events respectively to cause a start of conversion. The ETPS[SOCPSSEL] bit field determines whether SOCACNT2 and SOCAPRD2 take control or not. The ETPS[SOCACNT] counter and ETPS[SOCAPRD] period values behave similarly to the interrupt generator except that the pulses are continuously generated. That is, the pulse flag ETFLG[SOCA] is latched when a pulse is generated, but the interrupt generator does not stop further pulse generation. The enable and disable bit ETSEL[SOCAEN] stops pulse generation, but input events can still be counted until the period value is reached as with the interrupt generation logic. The event that triggers an SOCA and SOCB pulse can be configured separately in the ETSEL[SOCASEL] and ETSEL[SOCBSEL] bits. The possible events are the same events that can be specified for the interrupt generation logic with the addition of the DCAEVT1.soc and DCBEVT1.soc event signals from the digital compare (DC) submodule. The SOCACNT2 initialization scheme is very similar to the interrupt generator with respective enable, value initialize and SYNC or software force options.
Figure 14-48 shows the operation of the event-trigger's start-of-conversion-B (SOCB) pulse generator. The event-trigger's SOCB pulse generator operates the same way as the SOCA.