; Filename:     exceptions.s 
; Author:       ECE 353 student 
; Description:  exception handlers

	EXPORT  Undef_Handler
	EXPORT  SWI_Handler
	EXPORT  PAbt_Handler
	EXPORT  DAbt_Handler
	EXPORT  IRQ_Handler
	EXPORT  FIQ_Handler
	IMPORT 	Globals
	IMPORT  DisplayPrompt

	INCLUDE	aduc7026.inc

	AREA    FLASH, CODE, READONLY
	ARM

; dummy handlers for interrupts here
Undef_Handler
	MOVS	PC, LR
SWI_Handler
	MOVS	PC, LR
PAbt_Handler
	SUBS	PC, LR, #4
DAbt_Handler
	SUBS	PC, LR, #8
IRQ_Handler
    PUSH 	{R1,R7,LR}			;; Store context
	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
	LDR		R7, =(UART_MMR_BASE)
	LDR		R1, [R7,#COMRX]		;; read incoming byte
	CMP		R1, #0x0D
	BLEQ	DisplayPrompt
	STRNE	R1, [R7,#COMTX]		;; echo to screen
	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
	POP		{R1,R7,LR}			;; restore context
	SUBS	PC, LR, #4			;; return from interrupt
FIQ_Handler
	SUBS	PC, LR, #4


	END