Stack!!!

[tallht]

	processor pic16f877a
				include <p16f877a.inc>
		__config _xt_osc & _wdt_off & _cp_off & _boden_off & _lvp_off
;***********************************************************************
		#define read 	porte,0
		#define write	porte,1
		#define cs		porte,2
dataout		equ		0x20		;chua du lieu can doc boi master
w_save		equ		0x21
pc_lath		equ		0x22
status_save	equ		0x23
fsr_save	equ		0x24
;*********************chuong trinh ngat
		org 0x0004
		goto isr
;*********************
isr
;luu cac gia tri thanh ghi giong tac vu push
		movwf w_save
		swapf status,w
		movwf status_save
		movf pclath,w
		movwf pc_lath
		clrf pclath
		movf fsr,w
		movwf fsr_save

		btfss pir1,pspif		;kiem tra co ngat cua psp
		goto exit				;bang 0 thi thoat
		bcf pir1,pspif			;bang 1 thi xoa co ngat nay
		
		banksel trise			;quay ve thanh ghi trise	
		btfsc trise,obf			;kiem tra du lieu da duoc doc chua?
		Goto exit				;neu chua doc thi thoat ngat
		
		bcf status,rp0
		movf dataout,w			;chuyen du lieu tra portd
		movwf portd
exit							;phuc hoi gia tri ban dau cua cac thanh ghi
		bcf status,rp0
		movf fsr_save,w
		movwf fsr
		movf pc_lath,w
		movwf pclath
		swapf status_save,w
		movwf status
		swapf w_save,f			;swap 2 lan de khong thay doi cac co trong thanh ghi status
		swapf w_save,w
retfie
;*************************************************************************************
;chuong trinh chinh
		org 0x0000
		clrf status
		movlw 0x00
		movwf pclath
		goto main
;*************************************************************************************
main
		org 0x050
		banksel portd
		clrf portd
		banksel trise
		movlw b'00010111'
		movwf trise				;3 chan input,cho phep psp
		movlw 0x06
		movwf adcon1			;cac chan vao la digital
;***khoi tao ngat psp
		bsf pie1,pspie
		banksel intcon
		bsf intcon,gie			;cho phep ngat toan cuc
		bsf intcon,peie			;cho phep ngat psp
;khoi tao gia tri can doc boi master
		movlw b'01010101'
		movwf dataout
		movwf portd
;**************************************************************************************
		goto $
		end

đoạn code này dùng cho con slave trong chế độ psp