gdr@pbhya.UUCP (Guy Ridley) (01/20/88)
I am writing some music composition software. I want it to spend most of its time making up music, but then at regular intervals send the next note (or note-off message) out the MIDI port. I have read what ST Internals has to say about the clock interrupts, but since there is no example given, I am still murky about what I need to do and in what order. As I understand it, using the C timer, I am limited to intervals that are multiples of 1/200th second. Is this true? Also, I remember reading here that the 200hz clock is not always accurate. Is this so? And why? I understand that I have to mess with a vector, and then write a routine (that sends notes) at the place to which the new vector points (I assume by using another ORG in the assembler code?). But... how do I make sure that after that routine is done, the main part of the program continues exactly where it left off? I guess what I need is an example of code that uses a timer interrupt, or else a clear, thorough book on interrupts. Any suggestions?
brenes@sky.COM (Erasmo Brenes) (01/20/88)
Try looking at the MWC (Mark Williams C) manual. It shows some examples of using the timers to interrupt a program. I would recommend to use timer A which is reserved for user applications rather than timer C which is used elsewhere in the system. Also some of the examples that come with the package deal with handling system calls from a C language program. I hope this gives you some leads.