; **********************************************************************
; * File  S1DEB4.asm           board: GPC 553               with SXA51 *
; * GRIFO(R)   via Dell'Artigiano 8/6   40016 S. Giorgio di Piano (BO) *
; *     Tel. +39 051 892052                        Fax. +39 051 893661 *
; *     http://www.grifo.it                       http://www.grifo.com *
; *     by Alessio Francesconi                                28.09.04 *
; **********************************************************************
; DEB 01's example program of section 1, driven from a GPC 553. 
; This section is composed by 16 keys conncted to 16 LEDs:
; the pressure of one or more of these keys, sets the logic state 0 on
; the line and the relative LED is lit by hardware.
; This program has to comunicate with PC and to writes the status of 
; dip switch on port 0 (port 4 of GPC 553): in this case
; every dip switches combination, will modify the lighting of relative
; LEDs on port 0. Don't touch dip 5,6 and 7 of dip switch because they 
; can modify the board mapping.  
; For cursor movement and positioning, are used some command sequences
; with ADDS Viewpoint standard (see GET51 manual).
; The connection is realized through one 20 pins flat cable that interface
; CN5 connector of GPC 553 and CN15 connector of DEB 01.
;
;
;               Addresses of on board peripherals
;
              PORT1       EQU    090H              ;80c552 data register of port 1 
              PORT4       EQU    0C0H              ;80c552 data register of port 4
	      DSW1        EQU    0FFFCH		   ;80c552 data register of dip switch 
;
;              Initialization of constant data
;
              TXCHAR   EQU   0DH              ;variable with the value for the transmission
              FPORT    EQU   08H              ;internal memory address with port4 value
	      DIPS     EQU   0AH 	      ;internal memory address with dip switch value
              SECPORT  EQU   09H	      ;internal memory address with port1 value
;
;             Start of main program 
;
                ORG     2050H                   ;beginning of executable part program
MAIN:		MOV     SP,#2FH                 ;initialize the first free location pointer of the stack
		MOV	PORT4,#00H		;set port 4 GPC 553 (port 0 DEB 01) in output
		CLR	RS0			;select the registers bank 0 (00H-07H)
		CLR	RS1 
                ACALL   SERIAL
		MOV	DPTR,#HEADING		;print to monitor the "HEADING" string
		ACALL	STRING
;
;
CYCLE:          ACALL   INDSW1                  ;read dip switch
                MOV     FPORT,DIPS              ;transfer dip switch data in FPORT variable
                ACALL   OUTPORT0                ;write on port 0
                AJMP    CYCLE                   
;
;              Subroutine to acquire the reading data on dip switch                
;
INDSW1:   	PUSH	PSW			;save registers used by subroutine
		PUSH    DPL                     
                PUSH    DPH                     
                PUSH    ACC                     
                MOV     DPTR,#DSW1              ;load the dip switch address and 
                MOVX    A,@DPTR                 ;acquire its data
		MOV	DIPS,A			;save it on proper variable
	        POP     ACC                     ;restore registers used by subroutine
                POP     DPH                     
                POP     DPL                     
		POP	PSW			
		RET
;
;              Subroutine to show the acquire data on Port 0          
;
OUTPORT0:	PUSH	PSW			;save registers used by subroutine
		PUSH    DPL                     
                PUSH    DPH                     
                PUSH    ACC                     
		MOV	A,FPORT                 ;load the value to represent on ACC   
          	MOV	PORT4,A			;and to put it on port 0 of DEB 01
	        POP     ACC                     ;restore registers used by subroutine
                POP     DPH                     
                POP     DPL                     
		POP	PSW			
		RET
;
;             Serial initialization procedure
;
SERIAL:         PUSH	PSW			;save PSW
		MOV     SCON,#50H               ;select mode 1, active reception
	     	MOV     TH1,#253                ;initialize to 19200 baud
                ANL     PCON,#7FH               ;reset the bit 7 of PCON (SMOD)
		POP	PSW			;restore PSW
                RET
;
;             Serial transmission of a string contained in external data memory
;
STRING:  	PUSH	PSW			;save registers used by subroutine
		PUSH	ACC			
		PUSH	TXCHAR			
STRINGLOOP:     MOVX	A,@DPTR			;load into A the memory contents pointed by DPTR
		JZ	ENDSTRING		;if the last reading character is void (00H),jump to end
		MOV	TXCHAR,A		;put the current character into the variable for the transmission
                ACALL   TRASMSER      	 	;transmit the character
                INC     DPTR            	;increase the pointer to be ready 
                SJMP    STRINGLOOP     		;for the following character
ENDSTRING:	POP	TXCHAR			;restore registers used by subroutine
		POP     ACC             	
		POP	PSW			
                RET
;
;            Serial transmission's procedure
;
TRASMSER:	PUSH	PSW			;save PSW      
TRASM1: 	JBC     TI,TRASM2	 	;jump to TRASM2 if TI = 1 and reset TI
                SJMP    TRASM1  	       	;jump to TRASM1 because TI = 0
                                      	  	;and serial is still in transmission
TRASM2:   	MOV     SBUF,TXCHAR
		POP	PSW			;restore PSW
                RET
;
;
HEADING:        DB      0CH,' Writes to Port 0 the status of user dip switch, if present.',00H
                END