17.6 Interrupts
The interrupt sources within the PWM system are routed to the CPU in one of two ways:
- Through a shared signal for each PWM Generator (see Event Interrupts). The signals
include:
- EOC event
- TRIGA compare event
- ADC Trigger 1 event
- PCI_active event
- Through the PWM Event Output block (see PWM Event Outputs) are various sources of interrupts that can be generated by the PWM module.
For example, a device which has eight PWM Generators and six PWM event outputs would have a total of fourteen independent interrupt sources.
Since the PWM module can operate at a much higher frequency than the CPU system clock, care should be taken with the interrupt event configuration. Successive interrupt events on the same interrupt vector that occur at a rate greater than the CPU can detect and service them may result in missed processing and unexpected results. This limitation is dependent on the relationship of the system clock frequency, PWM operating frequency and the execution time of the Interrupt Service Routine (the number of instructions is irrelevant, what matters is how long the ISR takes to execute before it yields control back to the interrupted thread).
Interrupts from different sources that occur in close proximity to each other will also not be detected by the CPU as separate interrupt events. Therefore, it is good software practice to check the PWM status flags to differentiate a PCI interrupt event from a PWM time base interrupt. In some cases, it is desirable to separate different types of interrupt events that could be produced by the PWM Generator. When multiple PWM Generators have been synchronized together, it is possible to enable the time base interrupt on a separate PWM Generator that is synchronized to the host PWM Generator. Using this method, the time base interrupt can be serviced by a separate interrupt vector. It is also possible to bring various PWM event signals outside of the PWM module via the PWM Event blocks to an external off-chip destination (see PWM Event Outputs).