[Return to top] Z80 intel hex loader. By Lee Davison.

This short peice of code is an intel hex loader. Before the loader is called for the first time the serial port must be set up, in this case by calling SETBD. The main routine is INTLIN and never quits, you'll need to reset the Z80 to exit.

It was originally written to allow me to download code to my MPF 1P.

; This is a very short Intel hex loader. It assumes the record starts
; with ':' , that hex chars are 0-9 and A-F (not a-f) and does NO
; error checking whatsoever. It was shoehorned into the uProfessor ROM
; in the 86 free bytes between $06E1 and $0737 and is 86 bytes long.

; IO/M Addresses

; Assumes the uPF IO/M card is fitted. The UART is an 8251AF and the CTC
; is the standard Z80 type.

URTDA	EQU	60h		;8251 UART Data Port
URTCNT	EQU	61h		;8251 UART Control Port

CTC2	EQU	66h		;CTC Channel 2, Baud rate generator for UART

; Setup 8251 9600 baud 8N1

	LD	A,#47h		;Counter mode, TC follows, Reset channel
	OUT	(CTC2),A	;CTC2 is baud rate gen for 8251
	LD	A,#03h		;Time const for 9600 baud
	OUT	(CTC2),A	;
	LD	HL,RESTAB	;Reset sequence for 8251
	LD	B,#TABEND-RESTAB;Table length
	LD	C,#URTCNT	;Point to control port
	OTIR			;OUT and loop until done

; Get Intel hex record
; Short version - no checksum calculation.

	CALL	CHRRD		;Get chr
	CP	#':'		;Is it ':'?
	JR	NZ,INTLIN	;If not then next
	CALL	BYTERD		;Get record length
	LD	B,A		;Put in B
	CALL	BYTERD		;Get record address hi byte
	LD	H,A		;Put in H
	CALL	BYTERD		;Get record address lo byte
	LD	L,A		;Put in L
	CALL	BYTERD		;Ignore record type
	CALL	BYTERD		;Get record data byte
	LD	(HL),A		;Save byte to memory
	INC	HL		;Next address
	DJNZ	DATAIN		;Decrement count and jump if not finished
	JR	INTLIN		;Ignore checksum byte and [CR][LF]

; 8251 Character in

	IN	A,(URTCNT)	;Get status byte
	BIT	1,A		;Check buffer full bti
	JR	Z,CHRRD		;Not full so wait
	IN	A,(URTDA)	;Get byte from buffer
	RET			;

; Get 2 ASCII characters as hex byte

	LD	D,#00h		;Set up
	CALL	HEXCON		;Get byte and convert to hex
	ADD	A,A		;First nibble so
	ADD	A,A		;multiply by 16
	ADD	A,A		;
	ADD	A,A		;
	LD	D,A		;Save hi nibble in D
	CALL	CHRRD		;Get next chr
	SUB	#30h		;Makes '0'-'9' equal 0-9
	CP	#0Ah		;Is it 0-9 ?
	JR	C,NALPHA	;If so miss next bit
	SUB	#07h		;Else convert alpha
	OR	D		;Add hi nibble back
	RET			;

;Byte sequence to set up 8251

RESTAB:	DB	00h,00h,00h,40h,4Eh,37h

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Last page update: 9th July, 2002.