;ports
DH bit p3.2	;int0
DL bit p3.3	;int1


;bits
rfid_sense 	bit 0x00
rfid_flag_full 	bit 0x01
DH_DL_bit	bit 0x02

;variables
rfid_ptr	equ 0x30
rfid_bank	equ 0x31;0x32,0x33,0x34(total 4 ram locations)
buffer 		equ 0x34
pulse_cnt0	equ 0x35
pulse_cnt1	equ 0x36


	org 0000
	ljmp on_rst



	org 0003h	;int0 isr
	setb rfid_sense
	reti

	org 000bh	;timer0 isr
	lcall isr_t0
	reti

	org 0013h	;int1 isr
	setb rfid_sense
	reti


	org 0050h
on_rst:
	lcall all_init

main_loop:
	jb rfid_sense,collect_rfid
	jb rfid_flag_full,parse_rfid
	sjmp main_loop



;####################################################################################
collect_rfid:
	clr ea			;diasable all ints(global enable bit)
	clr ex0			;disable int0
	clr ex1			;disable int1
	jnb DH,$		;wait till it comes back to high,igonre first bit(parity bit)
	jnb DL,$		;wait till it comes back to high,igonre first bit(parity bit)
	lcall rfid_loop		;go collect the remaining bits 
	clr rfid_sense		;clear the flag
	ljmp main_loop		;go back to the main loop

rfid_loop:
	jnb DH,update_rfid_DH
	jnb DL,update_rfid_DL
	jnb rfid_flag_full,rfid_loop	;keep looping till all the 24 bits are collected(2 bist are ignored ->parity bits)
	ret

update_rfid_DH:
	setb ea			;interrupt golbal enable bit,enable timer0 int
	clr tr0			;stop timer0 for reload
	mov th0,#00		;reload the timer0
	mov tl0,#00		;reload the timer0
	setb tr0		;start the timer0 for 65 milli sec
	jnb DH,$		;wait till the DH goes back to high state
	setb DH_DL_bit		;
	sjmp backup_rfid	;store the received bit

update_rfid_DL:
	setb ea			;interrupt golbal enable bit,enable timer0 int
	clr tr0			;stop timer0 for reload
	mov th0,#00		;reload the timer0
	mov tl0,#00		;reload the timer0
	setb tr0		;start the timer0 for 65 milli sec
	jnb DL,$		;wait till the DH goes back to high state
	clr DH_DL_bit		;
	sjmp backup_rfid	;store the received bit

backup_rfid:
	inc pulse_cnt0
	inc pulse_cnt1
	mov a,buffer
	mov c,DH_DL_bit
	rrc a
	mov buffer,a
	mov a,pulse_cnt0
	cjne a,#8,chk1
		mov r0,rfid_ptr
		mov @r0,buffer
		inc r0
		mov rfid_ptr,r0
		mov buffer,#00
		mov pulse_cnt0,#00
chk1:
	mov a,pulse_cnt1
	cjne a,#24,backup_rfid_exit
		setb rfid_flag_full	;all the bits have arrived
		clr ea			;disable all int's
		clr tr0			;stop timer0
		mov pulse_cnt0,#00
		mov pulse_cnt1,#00
backup_rfid_exit:
	sjmp rfid_loop


;####################################################################################

;####################################################################################
parse_rfid:

	mov rfid_ptr,#rfid_bank		;get the base arrds of the rfid bytes(26 bits,4 bytes)
	mov r0,rfid_ptr
	mov a,@r0
	inc r0
	mov rfid_ptr,r0
	lcall convert;arugument in acc
	
	mov sbuf,r0			;first send the facility code
	jnb ti,$
	clr ti


	mov sbuf,r1
	jnb ti,$
	clr ti

	mov sbuf,r2
	jnb ti,$
	clr ti



	mov sbuf,#','			;delimiter
	jnb ti,$
	clr ti


	mov r0,rfid_ptr
	mov a,@r0
	inc r0
	mov rfid_ptr,r0
	lcall convert

	mov sbuf,r0			;send the higher part of the 16 bit card id
	jnb ti,$
	clr ti


	mov sbuf,r1
	jnb ti,$
	clr ti


	mov sbuf,r2
	jnb ti,$
	clr ti


	mov r0,rfid_ptr
	mov a,@r0
	inc r0
	mov rfid_ptr,r0
	lcall convert



	mov sbuf,r0			;send the lower part of the 16 bit card id
	jnb ti,$
	clr ti


	mov sbuf,r1
	jnb ti,$
	clr ti

	

	mov sbuf,r2
	jnb ti,$
	clr ti

	

	mov sbuf,#13			;carriage return
	jnb ti,$
	clr ti
	mov sbuf,#10			;line feed
	jnb ti,$
	clr ti



	clr rfid_flag_full		;clear to indicate that the 26 bits are parsed

	mov ie,#1000$0101b		;int0 and int1 enabled

	ljmp main_loop
;####################################################################################

;####################################################################################
all_init:
	mov ie,#1000$0101b	;int0 and int1 enabled
	setb tcon.0		;make int0 edge triggerd
	setb tcon.2		;make int1 edge triggered

	clr rfid_sense		;flag to indicate start of the 26 bits
	clr rfid_flag_full	;flag to indicate all 26 bits have arrived
	clr DH_DL_bit
	mov buffer,#00		;ponter to point one location in the 4 bytes
	mov rfid_ptr,#rfid_bank;4 memory locations to hold 26 bits
	mov pulse_cnt0,#00
	mov pulse_cnt1,#00

;timer0 intialise used to generate 65 milli sec
	mov tmod,#01h		;timer0 in mode1(16 bit timer)
	mov th0,#00
	mov tl0,#00	
;serial intialise for 9600 baud
	MOV	TMOD,#21H	;TIMER 1 , MODE 2(AUTO RELOAD) and timer0 in mode 1(16 bit timer)
	MOV	TH1,#0FDH	;9600 BAUD RATE
	MOV	SCON,#50H	;8 BIT,1 STOP, REN ENABLE
	SETB	TR1		;START TIMER 1

	ret

;####################################################################################

;####################################################################################
isr_t0:
	clr tr0
	mov th0,#00
	mov tl0,#00

	clr ti
	mov sbuf,#'T'
	jnb ti,$
	clr ti


	clr rfid_sense		;flag to indicate start of the 26 bits
	clr rfid_flag_full	;flag to indicate all 26 bits have arrived
	clr DH_DL_bit
	mov buffer,#00		;ponter to point one location in the 4 bytes
	mov rfid_ptr,#rfid_bank;4 memory locations to hold 26 bits
	mov pulse_cnt0,#00
	mov pulse_cnt1,#00

	mov ie,#1000$0101b	;int0 and int1 enabled
	ret
;####################################################################################


;@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
;THIS  WILL CONVER THE BINARY NUMBER IN ACCUMULATOR INTO ASCII
;ARGUMENT1 --> ACCUMULATOR ==>THE NUMBER TO BE CONVERTED
;RETURN  -->   R2 ==> UNITS PLACE
;	 -->   R1 ==> TENTS PLACE
;	 -->   R0 ==> HUNDREDS PLACE

CONVERT:
	MOV B,#10
	DIV AB
	MOV R2,B

	MOV B,#10
	DIV AB
	MOV R1,B

	MOV R0,A

	MOV A,#30H		;CONVERT THE BCD INTO ASCII
	ORL A,R2
	MOV R2,A		;R2 ==> UNITS PLACE

	MOV A,#30H		;CONVERT THE BCD INTO ASCII
	ORL A,R1
	MOV R1,A		;R1 ==> TENTS PLACE

	MOV A,#30H		;CONVERT THE BCD INTO ASCII
	ORL A,R0
	MOV R0,A		;R0 ==> HUNDREDS PLACE

	RET
;@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
end