irq_ven.s

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; ********************************************************************************
; *
; * ARM Strategic Support Group
; *
; ********************************************************************************

; ********************************************************************************
; *
; * Module      : irq_ven.s                   
; * Description : Angel IRQ veneer code                     
; *    
; *           This code is written to allow chaining of the
; *           example IRQ code with the Angel IRQ handler      
; *           caring for the registers using the stack.   
; *
; * Tool Chain	: ARM Developer Suite v1.0
; * Platform   	: Evaluator7T
; * History    	: 
; *
; * 	970326 DBrooke
; *		- created example code
; *
; * 	980420 MEchavarria
; * 	- modified for Sharp 77790A
; *     - added timer counter interrupt handler
; *
; *		980429 ASloss
; *		- added button interrupt handler
; *
; *		2000-04-04 Andrew N. Sloss
; *		- ported to the Evaluator7T
; *
; * Notes      :
; *
; *  The AREA must have 
; *  - the attribute READONLY, otherwise the linker will not
; *   place it in ROM.
; *  - the attribute CODE, otherwise the assembler will not
; *   let us put any code in this AREA
; *
; ********************************************************************************

; ********************************************************************************
; * IMPORT/EXPORT
; ********************************************************************************

	IMPORT irq_buttonpress
	EXPORT handler_irq
	EXPORT Angel_IRQ_Address
	EXPORT SetupSVC		; just a stub, angel's done the job already

SYSCFG		EQU  	0x03FF0000

	AREA	irq, CODE, READONLY

; ********************************************************************************
; * DATA
; ********************************************************************************

INTPND		DCD		0x03ff4004				;IRQ controller	status register address

; *********************************************************************************
; * ROUTINES
; *********************************************************************************

; -- irqHandler -------------------------------------------------------------------
;
; Description	: handles the IRQ interrupt and determines the source and then
;		  vectors to the correct interrupt rountine.
;

handler_irq
	STMFD	sp!, {r0 - r3, LR}		; Maintain Stack using APCS standard
	LDR 	r0, INTPND				; Get address of the IRQ status Reg 
	LDR 	r0, [r0]				; Read the status reg byte
	TST		r0, #0x0001				; Is it a button press ?
	BNE		handler_event_button	; Branch if button is pressed
	LDMFD	sp!, {r0 - r3, lr}		;If not then its an Angel request
	LDR 	pc, Angel_IRQ_Address	;remove the regs from the stack and call 
									;the routine
;
; **********************************************************************************
; EVENT: Button
; **********************************************************************************
;

handler_event_button
 	BL	irq_buttonpress			; if this point is reached then the irq is from the
 								; button
	LDMFD   sp!, {r0 - r3,lr}	; return from the irq_buttonpress routine - restore 
								; the registers 
	subs    pc, lr, #4 			; and return from the interrupt
		
SetupSVC
	MOV	pc, lr			; return


	AREA	var, DATA, READWRITE

Angel_IRQ_Address	
	DCD 0x00000000	;Scratch location for Angel IRQ Handler address


	END

; ***********************************************************************************
; * End of irq_ven.c 
; ***********************************************************************************