;---------------------------------------------------------------------
;                                    ;8位/8位除法子程序
;時間：2004年7月
;單位: 上海凌陽科技
;作者：周俊峰
;Email:zhoujf@sunplus.com.cn
;Tel:021-50804488 ext.6124
;
;                                    ;8位/8位除法子程序         
;入口參數：G_Dividend_Buffer    G_Divisor_Buffer
;;G_Temporary是被除數的一個臨時存儲變量          
;出口參數：G_Div_Result         G_Div_Result+1
;----------------------------------------------------------------------
.SYNTAX  6502   ;process standard 6502 addressing syntax
.LINKLIST       ;generate linklist information
.SYMBOLS        ;generate symbolic debug information
.PAGE0          ;define values in the range from 00h to FFh
.include        SPMC810A.inc

ORG     $80

G_Dividend_Buffer                  DS                 1;被除數
G_Divisor_Buffer                   DS                 1;除數
G_Div_Result                       DS                 2;結果
ShiftTimes                         DS                 1
G_Temporary                        DS                 1;臨時存儲變量


.CODE

ORG     $EE00		         				
.PUBLIC		V_Reset
V_Reset:
V_PowerOn:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
						sei
						ldx 	#C_STACK_BOTTOM ;set stack bottom
						txs                	; transfer x to  stack                        
                   
                        lda     #109
                        sta     G_Dividend_Buffer;裝入被除數低位數據
          
                        
                        lda     #10
                		sta     G_Divisor_Buffer;裝入除數低位數據
                		                		
                		lda     #0;清除結果單元
                		sta     G_Div_Result                		
                		sta		G_Temporary;臨時被除數清零
                		
		                lda		#8
		                sta		ShiftTimes	                     
                        
;---------------------------------------------------------
 
F_Div_Sub:
		lda		#00H
		sta		G_Div_Result
				
		sta     G_Temporary		 

		lda		#8
		sta		ShiftTimes					;設定除法需要移位的次數

		lda		G_Dividend_Buffer
		beq		L_Div_End					;被除數為0,返回
		sta		G_Dividend_Buffer
		
		lda		G_Divisor_Buffer
		beq		L_Div_End					;除數為0,返回
		sta		G_Divisor_Buffer

L_Shift_Div:		
		clc
		rol		G_Dividend_Buffer
		rol		G_Temporary					;被除數左移,被除數前面補一個八位的0		
		bcs		L_Result			        ;c=1;有溢出,說明被除數大，九位數比八位數大
		lda		G_Divisor_Buffer
		cmp		G_Temporary					 ;移位的被除數和除數的高位相比較
		bcc		L_Result					 ;除數小于臨時被除數,商上1
		beq		L_Result
		jmp		L_Div_NextBit                ;除數大于臨時被除數,商上0,即結果直接左移一位

L_Result:
		inc		G_Div_Result				 ;商上1
		lda		G_Temporary
		sec
		sbc 	G_Divisor_Buffer
		sta		G_Temporary

L_Div_NextBit:		
		dec		ShiftTimes
		lda		ShiftTimes
		beq		L_Div_End					 ;是否除完		
		clc
		rol		G_Div_Result	
		jmp		L_Shift_Div					 ;繼續除
		nop
		nop
		nop
L_Div_End:        
MainLoop:        
        nop
        nop
        nop
        nop
        nop
        jmp MainLoop
;=============================================================================
;    Interrupt   Subroutine
;=============================================================================				
V_IRQ:
		PHA
		TXA
		PHA

IRQ_END:
		PLA
		TAX
		PLA
		RTI
;=====================================================
;Description: 	NMI Interrupt Vector
;=====================================================
.PUBLIC	V_NMI
V_NMI:
		RTI
.ORG	$1FFA					;Define	two different areas since SICE
		DW	V_NMI				;FMay download program emulated	either
		DW	V_PowerOn			;FIn internal memory or	external memory
		DW	V_IRQ

.ORG	$7FFA					;For EPROM with	EV BRD.	IRQ. CPU, or EXT. CPU
		DW	V_NMI
		DW	V_PowerOn
		DW	V_IRQ

.ORG	$FFFA					;For ICE trace.
		DW	V_NMI
		DW	V_PowerOn
		DW	V_IRQ  		
.END