E9_E1.ASM

; Interface the keypad and read the key-codes (HEX) of all keys.
; Connect the keyboard to J2 of the trainer
; Set the trainer in to KEYBOARD MODE
; Configure Port A as Input and Port C as Output

; 8000H
BEGIN:
	MOV DPTR, #E803H 			; ADDRESS OF (J2) CONTROL REG
	; SET ALL PORTS AS INPUTS; PORT_A IN INPUT MODE
	MOV A, #90H 				; CONTROL CODE
	MOVX @DPTR, A 				; SET CONTROL REGISTER WITH THE CODE
	MOV A, #07H 				; TO SEND HIGH ON ALL ROWS
	DEC 82H 					; DEC DPTR
	MOVX @DPTR, A 				; WRITE TO PORT_C
	MOV 82H, #00H 				; GO TO PORT_A

WAIT1:
	MOVX A, @DPTR 				; GET PORT_A INPUT TO ACCUMULATOR
	; CHECK ALL KEYS RELEASED?
	JNZ WAIT1 					; REPEAT UNTILL NON-ZERO INPUT GIVEN
	LCALL DBOUNCE 				; AWAIT DEBOUNCE KEYBOARD

WAIT2:
	MOVX A, @DPTR 				; READ PORT_A FOR COLUMNS
	JZ WAIT2 					; CHECK ANY KEY PRESSED?
	LCALL DBOUNCE 				; AWAIT DEBOUNCE KEYBOARD
	MOV R0, #00H 				; INITIAL KEY CODE
	MOV R1, #03H 				; THE NUMBER OF ROWS
	MOV R2, #80H 				; TO SEND HIGH TO THE ROWS; INITIAL VALUE

NXT_ROW:
	MOV DPTR, #E802H 			; ADDRESS OF PORT_C
	MOV A, R2 					; GET HIGH CODE TO ACCUMULATOR
	RL A 						; ROTATE LEFT TO GO TO THE NEXT ROW
	MOV R2, A 					; SAVE IN (R2)
	MOVX @DPTR, A 				; WRITE IN PORT_C
	MOV DPL, #00H 				; GO TO PORT_A
	MOVX A, @DPTR 				; GET PORT_A INPUT
	JNZ FOUND 					; 
	MOV A, R0 					;
	ADD A, #08H 				;
	MOV R0, A 					;
	DJNZ R1, NXT_ROW 			;
	LJMP BEGIN 					; EXIT AND BEGIN AGAIN

FOUND:
	RRC A
	JC OVER
	INC R0
	SJMP FOUND

OVER:
	MOV 60H, R0 				; DISPLAY PLACEHOLDER
	MOV F0H, #00H 				; NO DOT
	LCALL UPDDT 				; SHOW IN DISPLAY FIELD
	LJMP BEGIN 					; REPEAT ENTIRE PROGRAM AGAIN

DBOUNCE:
	MOV TMOD, #10H 				; TIMER-1 IN MODE_1
	; DELAY OF 20ms
	MOV TH1, #B7H
	MOV TL1, #FFH
	SETB TR1 					; TIMER-1 SET

HERE:
	JNB TF1, HERE 				; WAIT UNTIL TIMER-1 OVERFLOWS
	; RESET TIMER-1
	CLR TF1
	CLR TR1
	RET 						; RETURN BACK TO MAIN LOOP