ORG 00H
	JMP init

	ORG 23H
	RETI

	ORG 30H
init:
	; serial port communication init
	MOV TMOD, #20H	; Timer 1 mode 2
	MOV TH1, #0FDH	; TH1 = FDH
	MOV SCON, #50H
	SETB TR1	; Start Timer 1
	
	; reserve bit addresing
	MOV SP, #2FH
	MOV R0, #00H

	; enable transmission and receiving
	CLR RI
	CLR TI

main:
	ACALL testclick
	ACALL testrecv
	JMP main

receive:
	JNB RI, $
	MOV A, SBUF
	CLR RI
	RET

transmit:
	MOV SBUF, A
	JNB TI, $
	CLR TI
	RET

testrecv:
	JNB RI, endre
	MOV A, SBUF
	CLR RI
	JZ off
	ACALL ledon
	AJMP endre
off:	ACALL ledoff
endre:	RET

testclick:
	; send 1 when button press, send 0 when button release
	MOV A, R0
	JNZ cur1
cur0:	JNB P2.3, send1
	AJMP endcl
cur1:	JB P2.3, send0
	AJMP endcl
send0:	MOV R0, #00H
	MOV A, #00H
	ACALL transmit
	ACALL blink
	AJMP endcl
send1:	MOV R0, #01H
	MOV A, #01H
	ACALL transmit
	ACALL blink
	AJMP endcl
endcl:	RET

hexprint:
	PUSH ACC
	MOV DPTR, #hex
	SWAP A
	ANL A, #0FH
	MOVC A, @A+DPTR
	ACALL transmit
	POP ACC
	ANL A, #0FH
	MOVC A, @A+DPTR
	ACALL transmit
	RET

ledon:
	CLR P2.5
	CLR P2.5
	RET

ledoff:
	SETB P2.5
	SETB P2.5
	RET

blink:
	ACALL ledon
	ACALL delay
	ACALL ledoff
	RET

delay:
	MOV R2,#07FH
	MOV R1,#0
d:	DJNZ R1, d
        DJNZ R2, d
	RET

hex:	DB "0123456789ABCDEF"

e:
	END