DDS (generating sine waves) with onboard DAC using latest PIC 16F chips?

[HenrikOlsson]

Ionnis, that's a very good point!
However, if DT-Ints are used it saves and restores those variables so I don't think there's any risk of corrupting them if an interrupt occurs during the calculation phase. (?)

If using ON INTERRUPT then you should definitely disable interrupts (or interrupt checking rather) during that calculation operation.

Hank, what you say is true but Ioannis has a point here. The R0/R2 variables are internal PBB variables used by a host of commands. If you're in the middle of that 32bit calculations and an interrupt comes along it's very likely that the code in the ISR uses those same variables (R0 and R2) so when you return the value previosuly there is now gone and you end up with weird results.

But like I said, the whole DT-Ints concept builds on saving the PBP system variables on ISR entry and restoring them on exit (if the handler is defined as PBP-handler) so I don't think it's going to be a problem.

Anyway, that calculation should only be executed when the frequency is changing so even if you SHOULD need to disable interrupts it won't make much difference.

/Henrik.

EDIT: Oooh, Hank, I think you're in for some trouble in the long run..... You have your handler defined as ASM yet we're doing a host of "PBP-work" in the handler. If you're not very carefull and know exactly what you're doing that is a very likely cause for trouble and data corruption due what is described above. Either write the handler in ASM or define as it type PBP and include the Re-Enter file.

EDIT2: Currently it might not be a problem since you're not doing anything in the main loop but as soon as you start doing things there it's going to go havoc.