;
;	This program is an asynchronous MASTER transmission and reception
;	through USART pin RC6 and RC7 with a data transfer of 1.2 kbps.
;	PIC16F877 with ST7537 powerline modem
;
;**************************************************************************************************
;
;	PROGRAMMED BY: 		JOHN PAUL S. AGUILING
;
;	DATE PROGRAMMED:	JULY 28, 2002
;
;	LAST UPDATED:		AUGUST 10, 2002
;
;	PROGRAM DESCRIPTION:
;
;	This is the second slave of the three powerline communication using 
PIC16F877.
;	This acquires ADC when called by the master and transmits back the value
;	to the master after the first slave transmits its data.
;	It repeats the process whenever called. Therefore this is part of the
;	system which acquires analog signal maximum is +5V.
;
;**************************************************************************************************

	LIST		P=16F877
	ERRORLEVEL 	-302
	#INCLUDE	P16F877.INC

	__CONFIG _CP_OFF & _XT_OSC & _WDT_ON & _WRT_ENABLE_ON & _PWRTE_ON & 
_LVP_OFF & _CPD_OFF & _DEBUG_OFF & _BODEN_OFF

	CBLOCK 20H
		TEMP
		PREAMBLE
		ACQUIRE
		ADDRESS
		ADDRESS_X
		ADC_REG
		DUMMY
		TWENTYMS
		SAMPLE
		COUNT
		RXTEMP
		NaHi
		NaLo
		NbHi
		NbLo
		d1
		d2
		GAP

	ENDC

INIT

        ORG 0x0000      ; start address = 0000h

; INITIALISE PORTS
; binary used to see individual pin level
; all port pins = low

	BCF	STATUS, RP0
	BCF	STATUS, RP1
	CLRF	PORTA
        CLRF	PORTB
	CLRF	PORTC
	CLRF	PORTD
	CLRF	PORTE

; INITIALISE PORTS for Receive
; binary used to see individual pin IO status

        bsf STATUS,RP0  ; set RAM Page 1 for TRIS registers

        movlw b'11000001'       ; all IO pins = outputs
        movwf TRISA
        movlw b'00000000'
        movwf TRISB
	movlw b'10100000'
	movwf TRISC
        movlw b'00000000'	; input
        movwf TRISD		; port D is input
        movlw b'11111000'
        movwf TRISE

        movlw b'00001110'       ; pin 1 analog, the rest digital
        movwf ADCON1

	BCF	STATUS, RP0

; INITIALISE USART for Receive

	bsf	STATUS, RP0
	movlw	d'207'
	movwf   SPBRG
	movlw   b'00100100'     ; brgh = 1
     	movwf     TXSTA           ; enable Async Transmission, set brgh
	banksel RCSTA       	; bank0
	movlw     b'10010000'
	movwf     RCSTA         ; enable Async Reception
	movf RCREG,w
	movf RCREG,w
	movf RCREG,w     	; flush receive buffer

START
	bcf	STATUS, RP0
	bcf	STATUS, RP1
	CLRF	ADDRESS
	CLRF	ADC_REG
	CLRF	RCREG
	movlw	b'11111111'
	movwf	PREAMBLE
	movlw	b'11000011'
	movwf	ACQUIRE
	MOVLW	d'10'
	MOVWF	GAP
	goto	MAIN

RecLoop

	nop
	btfss   PIR1,RCIF ; check for received data
	goto 	RecLoop
	movf 	RCREG,w
	return

TxLoop

     	nop
	btfss     PIR1,TXIF ;xmit buffer empty?
	goto TxLoop         ;no, wait
	return

TxData

	BTFSS	PORTC, 5	; CHECK CD
	GOTO	TxData
	BCF	PORTC, 4	; TRANSMIT MODE
	CALL	DELAYMS
	MOVF	PREAMBLE, W
	MOVWF	TXREG
	CALL	TxLoop
	MOVF	ACQUIRE, W
	MOVWF	TXREG
	CALL	TxLoop
	MOVF	ADDRESS, W
	MOVWF	TXREG
	MOVWF	PORTD
	CALL	TxLoop
	MOVF	ADC_REG, W
	MOVWF	TXREG
	CALL	TxLoop
	CALL	DELAYMS
	MOVLW	b'10010011'
	MOVWF	PORTC

	RETURN


; 1/2 SEC DELAY ROUTINE WITH 4MHz CLOCK

DELAY
	movlw 01h
        movwf NbHi
        movlw 03h
        movwf NbLo
        movlw 8Ah
        movwf NaHi
        movlw 5Bh
        movwf NaLo

DeLoop  decfsz NaLo,F
        goto DeLoop
        decfsz NaHi,F
        goto DeLoop
        decfsz NbLo,F
        goto DeLoop
        decfsz NbHi,F
        goto DeLoop

	RETURN

Delayms
			;19993 cycles
	movlw	0x9E
	movwf	d1
	movlw	0x10
	movwf	d2
Delay_0
	decfsz	d1, f
	goto	$+2
	decfsz	d2, f
	goto	Delay_0

			;3 cycles
	goto	$+1
	nop

			;4 cycles (including call)
	return

DELAYVIEW
	CALL	DELAY
	DECFSZ	GAP, F
	GOTO	DELAYVIEW
	MOVLW	d'10'
	MOVWF	GAP
	RETURN

;
;
; ------------------------------------
; PROVIDE A SETTLING TIME FOR START UP
; ------------------------------------
;

MAIN
        clrf temp
Settle
        decfsz  temp, f
        goto Settle

	MOVLW	b'10010011'
	MOVWF	PORTC

ReceiveADC
	CLRWDT
	MOVLW	b'00111100'
	MOVWF	ADDRESS_X
        call    RecLoop         ; wait and read from PLM-24
	movwf	RXTEMP
        movwf   PORTD          ; show value for diagnostic purpose
	XORWF	ACQUIRE, W
	BTFSS	STATUS, Z
	GOTO	ReceiveADC
	CALL	RecLoop
	MOVWF	ADDRESS
	XORWF	ADDRESS_X, W
	BTFSS	STATUS, Z
	GOTO	DISCARD
	CLRF	RCREG

; ------------------
; PERFORM ADC NOW!!!
; ------------------

	MOVLW	b'01000011'
	MOVWF	ADCON0
	MOVLW	b'00011001'
	MOVWF	TWENTYMS
	NOP
	NOP
	NOP
TWENTY	DECFSZ	TWENTYMS,F
	GOTO	TWENTY
	BSF	ADCON0, GO
	NOP
	NOP
ANDICO	BTFSC	ADCON0, GO
	GOTO	ANDICO
	MOVF	ADRESH, W
	MOVWF	SAMPLE
	MOVWF	PORTD
	BSF	PORTC, 2
	CALL	DELAY


; ----------------------------------
;	Identification for Slave B
; ----------------------------------

	MOVLW	b'11110000'
	MOVWF	ADDRESS_X

;==============================

ReceiveME
	CLRWDT
        call    RecLoop         ; wait and read from PLM-24
	movwf	RXTEMP
        movwf   PORTD           ; show value for diagnostic purpose
	XORWF	ACQUIRE, W
	BTFSS	STATUS, Z
	GOTO	ReceiveME
	CALL	RecLoop
	MOVWF	ADDRESS
	XORWF	ADDRESS_X, W
	BTFSS	STATUS, Z
	GOTO	DISCARD
	BSF	PORTC, 1
	CLRF	RCREG
	CALL	DELAY
	GOTO	Transmit

DISCARD
	CALL	RecLoop
	MOVWF	DUMMY
	GOTO	ReceiveME

Transmit
	CLRWDT
	CALL	DELAY
	CALL	TxLoop
	MOVF	ADDRESS_X, W
	MOVWF	ADDRESS
	MOVF	SAMPLE, W
	MOVWF	ADC_REG
	CALL	TxData
	CLRF	RCREG
;	CALL	DELAY

	GOTO	MAIN

	END