RE: M68K C Interrupt Handler

["Robert Grand" <RobertGrand at wanadoo dot fr>]

> Does anyone know how to write  m68k interrupt handlers  in C?  My
> (possibly
> incorrect/incomplete) understanding of the  issues are that:
> (1) Normal  function calls generated by the compiler will not work as
> interrupt functions,
> (2) I need to save all registers,
> (3) I can now execute my handler specific C code including any HW specific
> start-of-interrupt and end-of-interrupt processing,
> (4) I need to restore registers,
> (5) I need to do a return from interrupt (rte).

For m68k-coff projects, I have only one assembly file which contains:
- vector table
- first level exception handlers
- bss section initialization

Vector table looks like:
/*-------------------------------------------------------------
-------------------------------------------------------------*/
		.include		"m68332.d"
		.section		.text
		.long			SystemStackTop
		.long			ResetHandler
	other entries
		.globl		Level1AutoVectorHandler
	other entries

First level exception handlers looks like:
/*-------------------------------------------------------------
-------------------------------------------------------------*/
Level1AutoVectorHandler:
		movem.l		%d0-%d1/%a0-%a1,-(%a7)
		jsr			Spc3_IrqHandler
		movem.l		(%a7)+,%d0-%d1/%a0-%a1
		rte
You don't need to save other registers here. Spc3_IrqHandler is a C function
whose prototype is void Spc3_IrqHandler( ).

BSS section initialization:
/*-------------------------------------------------------------
-------------------------------------------------------------*/
		.even
		.globl		ResetHandler
ResetHandler:
		movea.l		#SystemStackTop,%ssp
		move.l		#__bss_start,%a0
		move.l		#_end,%a1
2:
		cmp.l			%a0,%a1
		beq.s			1f
		clr.b			(%a0)+
		bra.s			2b
1:
		jsr			main
		illegal



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