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Sometimes DIVSION doesn't work in Dallas 390

Mike Hwang

This is a test project in Dallas 390 and the target options-Use On-chip Arithmatic Accelerator is selected
main.c: 

void main(void)
{
	unsigned int i = 2008;
	unsigned char ch;

	ch = i%100;
	ch = i/100;
}
I can get the right answer in this test project,and I can't in my original project which include some other modules.But if I unselect target options-Use On-chip Arithmatic Accelerator,I can get the right answer.There maybe something I don't know about Arithmatic Accelerator in Dallas 390.Anybody can give me the answer?Thanks!

  • 0

    You didn't get any answer so far, likely because you chose the wrong product family (C251).

    That said, it's quite impossible to guess what went wrong in your actual code if you don't show any of that. Code that does work doesn't explain anything about other code that doesn't.

    Just one hint: did you check the "ANSI C integer promotion rules" option?

  • 0

    The Compiler User's Guide suggests the following:

    Use the following suggestions to help guarantee that only one thread of execution uses the arithmetic processor:

    • Use the MODDA directive to compile functions which are guaranteed to execute only in the main program or functions used by one interrupt service routine, but not both.

    • Compile all remaining functions with the NOMODDA directive.

    Is it possible that in your program you use the arithmetic accelerator in an interrupt and in the main program and that the math operations in the man program get interrupted (by the interrupt) and corrupted?

    Jon