;==================================================================================
; The information contained herein is the exclusive property of
; Sunplus Technology Co. And shall not be distributed, reproduced,
; or disclosed in whole in part without prior written permission.
;       (C) COPYRIGHT 2004   SUNPLUS TECHNOLOGY CO.                                  
;                   ALL RIGHTS RESERVED
; The entire notice above must be reproduced on all authorized copies.
;==================================================================================
										
;==================================================================================
;	Project Name	:	
;	Applied Body	:	SPMC65P2404A
;	Firmware version:
;	Programer		:
;	Date			:	2004-8-30
;	Description		:	This program presents an example that how to use stack.
;						
;	Hardware Connect:	
;	Link File		:	
;	IDE Version		: 	V1.6.5	
;	BODY Version	:	V1.0.0A
;=================================================================================

.SYNTAX  6502							;process standard 6502 addressing syntax
.LINKLIST								;generate linklist information
.SYMBOLS								;generate symbolic debug information
;************************************************************************************
;*																					*
;*      System Register Define	                                                    *
;*																					*
;************************************************************************************
.INCLUDE		SPMC65P2404A.inc				;Define all hardware,Registers and ports. 
;************************************************************************************

;************************************************************************************
;*																					*
;*      Data memory Define	                                                        *
;*																					*
;************************************************************************************
.PAGE0									;define values in the range from 00h to FFh
;************************************************************************************
.DATA									;define data storage section
;************************************************************************************
;*																					*
;*      	 Program Area															*
;*																					*
;************************************************************************************
.CODE
          
;************************************************************************************
;*																					*
;*      Power on Reset Process	                                                    *
;*																					*
;************************************************************************************
V_Reset:
		sei								;Disable interrupt
		ldx		#C_STACK_BOTTOM			;Initial stack pointer at $01FF
		txs								;Transfer to stack pointer
		jsr		F_Tim0_Init
		cli								;Enable interrupt
?L_Main_Loop:							;the example for test   
		;==============================================================
		;stack pointer is extended from $01FF to $01E0,when data pushed 
		;onto stack,stack pointer will decrease by 1,when data is poped 
		;from stack,stack pointer is increased by 1.stack has the 
		;property that the last item placed on the stack will be the 
		;first item removed(last in,first out). 
		;============================================================== 
		lda		#$34
		ldx		#$90
		pha				;Push A register,then sp<=sp-1.	
		txa
		pha				;Push X register,then sp<=sp-1.		
		lda		#$23
		ldx		#$44	
		pla				;\ first sp<=sp+1,then pop X register,the value 
		tax				;/ of X is #$90.
		pla				;first sp<=sp+1,then pop A register,the value 
						;of A is #$34.
		;==============================================================
		;push and pop status register
		;==============================================================
		clc
		php				;Push status register,then sp<=sp-1.	
		sec
		plp				;first sp<=sp+1,then pop status register,the carry 
						;flag is "0".
		
		;==============================================================
		;when jump to a subprogram,stack is used for storing return 
		;address
		;==============================================================
		jsr		F_1		;before jump is performed,stack is used for storing 
						;return address:an address location where the  
						;instruction"jsr	F_1" is held.first,push the high 
						;8bit address, then (sp<=sp-1);second,push the low 
						;8bit address,then (sp=sp-1). 
						
		jmp		?L_Main_Loop      
		
        ;==============================================================
		;when return from a subprogram,SP pop return address
		;==============================================================
F_1:
		nop				;for user
		rts				;before the subprogram return,first sp<=sp-1,
						;then SP pop the low 8bit address,second,
						;sp=sp-1,then pop the high 8bit address 
;====================================================================
;	Function:			F_Tim0_Init
;	Description:		Set 4ms interrupt in timer0 
;	Input:				none
;	Output:       		none
;	Destroy:			A
;	Stacks:				1
;====================================================================
F_Tim0_Init:	 
		lda		#C_T08B_Timer				;Timer0 Function as  8 Bit Timer
		sta 	P_TMR0_1_Ctrl0
		lda 	#C_T0FCS_Div_128			;DIV=1/128
		sta		P_TMR0_1_Ctrl1
		
		lda 	#6  	 					;Preload counter= 166
		sta 	P_TMR0_Preload 				;8000000/128/250=250Hz=4ms
		
		lda		#C_INT_T0OIE
		sta		P_INT_Ctrl1					;Timer0 overflow INT enable
			
		lda 	#$FF					
		sta 	P_INT_Flag1 				
		rts


;**********************************************************************************
;*                                                                                *
;*      Interrupt Vector Table                                                    *
;*                                                                                *
;**********************************************************************************
		;=================================================================
		;when interrupt coming on,the return address and status register 
		;are pushed into stack.push the high 8bit address firstly,then 
		;(sp<=sp-1);push the low 8bit address secondly,then (sp=sp-1);
		;push the status register thirdly,then (sp=sp-1).
		;=================================================================
V_IRQ:      
		pha		                 
		txa						;Push A register,then sp<=sp-1.
		pha						;Push X register,then sp<=sp-1.
		
		lda		 P_INT_Flag1
		and		 #C_INT_T0OIF	;4ms INT comming?
		bne		 ?L_Timer0		;yes	
	    jmp      L_IntExit
        
?L_Timer0:		
        nop       				;for user    
L_IntExit:
		lda		 #C_INT_T0OIF
		sta		 P_INT_Flag1     
		pla						;\ sp<=sp+1,then pop X register
		tax						;/							
		pla						;sp<=sp+1,then Pop A register 
		rti						;before interrupt return,
								;first sp<=sp-1,pop the status register;
								;second sp<=sp-1,pop the low 8bit address;
								;third sp<=sp-1, pop the high 8bit address.		
		
V_NMI:
        rti
        
VECTOR		.SECTION
;*********************************************************************************
        DW      V_NMI             ; may download program emulated either
        DW      V_Reset           ; in internal memory or external memory
        DW      V_IRQ             ; dw define two bytes interrupt vector
;**********************************************************************************
;*                                                                                *
;*      End of Interrupt Vector Table                                             *
;*                                                                                *
;**********************************************************************************
.END