;
; This program, originally available on the Motorola DSP bulletin board,
; is provided under a DISCLAIMER OF WARRANTY available from Motorola DSP
; Operation, 6501 William Cannon Drive, West, Austin, Texas  78735-8598.
;
;	Serial Loader for the DSP56000.
;	This loader initializes the serial communications interface (SCI)
;	on the DSP56001 for 9600 baud and then loads OMF records (output
;	by the DSP56000 assembler) into internal memory.  The loader takes
;	the upper 128 bytes of P memory allowing the lower memory from
;	$0000-017F to be used by the user.  The following records are
;	interpreted:
;	    _DATA X ADDR
;	    _DATA Y ADDR
;	    _DATA P ADDR
;	    _END ADDR
;	After the END record is encountered, the loader jumps to the address
;	in the END record.  Note that an address MUST be present in the
;	END record (the program must contain at least one P segment).
;
;	To generate a EPROM of this loader (8Kx8), perform the following:
;	$ asm56000 -b -l -a sloader
;	$ srec sloader
;
;	The EPROM is in file SLOADER.P.  To program the EPROM, set the
;	programmer to MOTOROLA S record format, download the file with
;	a zero address offset and program the part.
;
;	The loader loads the following memory spaces:
;	    X - 0 to FF
;	    Y - 0 to FF
;	    P - 0 to 17F
;
	PAGE	132,60,1,1

SCR	EQU	$FFF0		;SCI CONTROL REGISTER
SCCR	EQU	$FFF2		;SCI CLOCK CONTROL REGISTER
PCC	EQU	$FFE1		;PORT C CONTROL REGISTER
RDRF	EQU	$2		;RECEIVE DATA REGISTER FULL FLAG
SSR	EQU	$FFF1		;SCI STATUS REGISTER
SRXH	EQU	$FFF6		;SCI RECEIVE IN HIGH BYTE
LDRMEM	EQU	$180		;START OF LOADER IN P MEMORY

	ORG	P:$0000		;RESET VECTOR FOR BOOTING
RVEC
	JMP	LOAD		;GO EXECUTE LOADER

	ORG	P:LDRMEM,P:3*LDRMEM
LOAD
	MOVEP	#$0302,X:SCR	;ENABLE TX,RX: 8 BIT 1 START, 1 STOP
	MOVEP	#$002A,X:SCCR	;CD=42 (/43), INT CLK @ 9600 BAUD (27MHz)
	MOVEP	#$0007,X:PCC	;ENABLE SCI
WTUS
	JSR	GETCH		;INPUT CHARACTER
	MOVE	#'_',X0		;GET UNDERSCORE CHARACTER
	CMP	X0,A		;SEE IF "_" YET
	JNE	WTUS		;NO
GOTUS
	JSR	GETCH		;GET A CHARACTER
	MOVE	#'D',X0		;GET A D FOR DATA
	CMP	X0,A	#'E',X0	;COMPARE TO D, GET E
	JEQ	DATAREC		;IF "D", THEN DATA RECORD
	CMP	X0,A		;SEE IF END RECORD
	JNE	WTUS		;NO, GO WAIT FOR ANOTHER UNDERSCORE
_WTSPC
	JSR	GETCH		;GET CHARACTER
	MOVE	#$20,X0		;GET SPACE
	CMP	X0,A		;WAIT FOR SPACE AFTER "END"
	JNE	_WTSPC		;WAIT FOR SPACE
	JSR	IN4		;GET TRANSFER ADDRESS
	MOVE	B1,R0		;MOVE TRANSFER ADDRESS
	NOP			;CLEAR ADDRESS PIPE
	JMP	(R0)		;GO EXECUTE USER CODE
DATAREC
	JSR	GETCH		;GET CHARACTER
	MOVE	#$20,X0		;GET SPACE
	CMP	X0,A		;SEE IF SPACE
	JNE	DATAREC		;NO
	JSR	GETCH		;GET [P,X,Y]
	MOVE	A1,Y0		;SAVE CHARACTER
	JSR	IN4		;GET ADDRESS OF DATA RECORD
	MOVE	B1,R0		;SAVE ADDRESS
	MOVE		#'X',A	;GET X
	CMP	Y0,A	#'Y',A	;SEE IF X, GET Y
	JEQ	_LDX		;LOAD DATA INTO X MEMORY
	CMP	Y0,A		;SEE IF Y
	JEQ	_LDY		;LOAD DATA INTO Y MEMORY
_LDP
	JSR	IN6		;GET DATA
	MOVE	B1,P:(R0)+	;LOAD P MEMORY
	JMP	_LDP
_LDX
	JSR	IN6		;GET DATA
	MOVE	B1,X:(R0)+	;LOAD X MEMORY
	JMP	_LDX
_LDY
	JSR	IN6		;GET DATA
	MOVE	B1,Y:(R0)+	;LOAD Y MEMORY
	JMP	_LDY

GETCH
	JCLR	#RDRF,X:SSR,*	;WAIT FOR DATA IN SCI
	MOVEP	X:SRXH,A	;GET SCI DATA IN HIGH BYTE
	LSL	A		;SHIFT OUT PARITY
	LSR	A		;PUT 0 IN PARITY BIT
	MOVE	A1,A		;SIGN EXTEND AND ZERO
	RTS

IN4
	CLR	B	#>4,X0	;CLEAR VALUE, GET 4
	JMP	READHEX		;READ 4 HEX CHARACTERS
IN6
	CLR	B	#>6,X0	;CLEAR VALUE, GET 6
READHEX
	DO	X0,_READHEX	;READ ASCII HEX AND CONVERT TO BINARY
_GET
	JSR	GETCH		;GET A CHARACTER
	MOVE	#'_',X0		;GET UNDERSCORE
	CMP	X0,A	#'F',X0	;SEE IF UNDERSCORE
	JNE	_NOTUS		;NO
	ENDDO			;EXIT LOOP
	MOVE	SSH,X0		;POP RETURN ADDRESS
	JMP	GOTUS		;GO PROCESS NEW INPUT RECORD
_NOTUS
	CMP	X0,A	#'0',X0	;SEE IF GREATER THAN F
	JGT	_GET		;YES, IGNORE
	CMP	X0,A		;SEE IF LESS THAN 0
	JLT	_GET		;YES, IGNORE
	SUB	X0,A	#10,X0	;ADJUST FOR ASCII TO BINARY
	CMP	X0,A	#7,X0	;SEE IF A-F
	JLT	_NOTALPHA	;NO
	SUB	X0,A		;ADJUST FOR 1-F
_NOTALPHA
	REP	#4		;SHIFT OLD VALUE LEFT 1 NIBBLE
	LSL	B
	REP	#16		;SHIFT NEW NIBBLE DOWN TO LSB
	LSR	A
	ADD	A,B		;ADD NEW NIBBLE IN
_READHEX
	RTS

	END