;******************************************************************************
;
;  PC2Flop - Transfer disk image from PC to floppy over serial port.
;
;	This program writes a Micropolis floppy disk from a disk image
;	transmitted from a PC. The image is transmitted through a serial
;	port using the XMODEM checksum protocol. The disk is written in
;  	raw format (270 bytes per sector, 16 sectors per track, 
;	77 tracks).
;
;	This program assumes the console port and the transfer port
;	are not the same device.
;
;	This program runs standalone at 0x100 or under CP/M. The program
;	is exited with a CTRL-C and either warm boots CP/M or exits to
;	the VG ROM monitor. 
;
;	The disk image format matches the Vector Graphic Image (VGI) format
;	defined by Howard Harte for his VG work on the Simh emulator. Each
;	sector in the PC file is 275 bytes in length, organized as follows:
;
;	Length	Content
;	   1	Sync byte (always 0xff)
;	   1	Track number (0-76)
;	   1	Sector number (0-15)
;	 266	Sector data payload (CP/M uses last 256 bytes of this)
;	   1	Checksum
;	   4	ECC for HD-FD controller (not used by floppy, set to zero)
;	   1	ECC valid flag (not used by floppy, set to zero)
;
;	Written by Mike Douglas
;
;	Rev	 Date	    Desc
;	1.0	05/27/14    Original
;
;	1.1	11/19/14    Use generic algorithms for buffering disk
;			    and XMODEM I/O to handle sector sizes that
;			    aren't multiples of the 128 byte XMODEM
;			    packet. Not really needed for the Northstar,
;			    but it makes this code more portable. Change
;			    drive validation, console I/O, serial I/O,
;			    etc. to make as common an interface as 
;			    possible for different platforms.
;
;	1.2	12/2/14     Ctrl-C during transfer returns to main menu
;			    instead of exiting. CR required after answering
;			    drive and port prompts. Check for 5 jumps of
;			    a jump table in chkCpm.
;
;	1.3	8/13/15	    Increase time from drive selection until
;			    I/O begins from the VG and Micropolis default
;			    of 250ms up to 750ms. This code can end up
;			    writing very quickly without reading track/sector
;			    ID's and takes the first sector that comes around,
;			    so this delay ensures a good quality write.
;
;	1.4	5/10/20     Add support for a third serial port at 6/7.
;
;*****************************************************************************

; VG Monitor Locations

VGMON	equ	0e000h		;base address of VG monitor
MONIT	equ	VGMON+0		;monitor entry point

; Disk information equates

NUMTRK	equ	77		;number of tracks
NUMSEC	equ	16		;number of sectors per track
SECLEN	equ	275		;sector length (as transmitted)
MINDRV	equ	0		;first drive number
MAXDRV	equ	3		;max drive number 

TRKLEN	equ	(NUMSEC*SECLEN)	;length of track in bytes
RDTRIES	equ	5		;number of read (verify) attempts
WRTRIES	equ	4		;number of write attempts

; Monitor, CP/M boot entry points

MONITOR	equ	MONIT		;ROM monitor entry point (stand alone mode)
CPMBOOT	equ	0f800h		;cold boot ROM entry point

; XMODEM equates

PKTLEN	equ	128		;128 byte xmodem packet length
SOH	equ	001h
EOT	equ	004h
ACK	equ	006h
NAK	equ	015h
EOF	equ	01ah		;ctrl-z character

; CP/M Equates

WBOOT	equ	0		;warm boot jump location

; Misc equates

CR	equ	13		;ascii for carriage return
LF	equ	10		;ascii for line feed
DEL	equ	7fh		;ascii DEL
BS	equ	08h		;ascii backspace
CTRLC	equ	03		;ascii for control-c
JMPINST	equ	0c3h		;jump instruction opcode

	org	0100h	
;-----------------------------------------------------------------------------
;  Initialize for transfer
;-----------------------------------------------------------------------------
init	lxi	sp,ourStk	;initialize stack pointer
	call	chkCpm		;set flag for CP/M or not
	call	sizeRam		;determine amount of RAM available
	mvi	a,MINDRV	;a=default drive
	sta	drvNum		;need for pgmExit

;  Display welcome message, then get the drive number and port number
;    to use for the transfer from the operator.

	lxi	h,mWelcom	;display welcome message
	call	dispMsg

; getDrv - get drive number or letter from the user.

getDrv	lxi	h,mDrive	;display drive number prompt
	call	dispMsg
	call	rcvCon		;get byte from the console
	ori	20h		;upper case letters to lower case
	cpi	'x'		;exit requested?
	jz	pgmExit		;yes
	lxi	h,baseDrv	;ascii 1st drive - baseDrv = 0
	sub	m
	jm	getDrv		;error, entry was < first drive
	cpi	MAXDRV-MINDRV+1	;validate <= max drive
	jnc	getDrv		;invalid, prompt again
	adi	MINDRV		;restore offset of 1st drive (if any)
	sta	drvNum		;save the drive number to use

; Verify drive is not write protected

	call	dRestor		;restore to track 0 (selects drive)
	call	dChkWP		;check write protect (aborts to getDrv)

; getPort - get pseudo port number 1-3 from the user.

getPort	lxi	h,mPort		;display transfer port prompt
	call	dispMsg
	call	rcvCon		;get byte from the console
	ori	20h		;upper to lower case, nums not affected
	cpi	'x'		;exit requested?
	jz	pgmExit		;yes
	sui	'1'		;'1' goes to binary 0
	cpi	3		;validate >='1' and <= '3'
	jnc	getPort		;invalid, prompt again
	rlc			;2 bytes per port
	adi	2		;first port is 2, gives 2, 4 or 6
	sta	siData+1	;patch data port references in code
	sta	soData+1
	inr	a		;address of status port
	sta	serIn+1		;patch status port references in code
	sta	serOut+1

; Prompt the user to insert the disk to write, initialize, then start
;   sending NAK to start the XMODEM reception.

	lxi	h,mStart	;display start file transfer prompt
	call	dispMsg
	mvi	a,0ffh		;init disk driver track number
	sta	curTrk		;to "invalid"
	xra	a		;init track we're reading to zero
	sta	trkNum
	inr	a		;init xmodem block number to one
	sta	blkNum
	lxi	h,trkBuf	;trkBuf is initial starting point for
	shld	rcvPtr		;   XMODEM receive
	mvi	a,NAK		;send starting nak after purging input data
	call	purgSio

;-----------------------------------------------------------------------------
;  mainLp - Receive as many packets as will fit into RAM and then write
;      tracks to disk. Repeat until entire disk is written. 
;-----------------------------------------------------------------------------
mainLp	call	bufPkts		;buffer as many packets as possible
	xchg			;de=start of last packet received
	lxi	h,trkBuf	;hl=start of track buffer
	shld	trkPtr		;writing will start from here
	call	cmpDeHl		;compare last packet start - trkBuf
	jc	allDone		;nothing received but an EOT

; trkLoop - write tracks until all disk tracks have been written or all
;    the tracks in the buffer have been written.

trkLoop	call	wrtTrk		;write a track (hl returns->next track)
	lda	trkNum		;increment track number (preserve HL)
	inr	a
	sta	trkNum	
	cpi	NUMTRK		;done all tracks?
	jz	allDone		;yes
	xchg			;de=next track pointer
	lhld	rcvPtr		;hl=start of last packet received
	call	cmpHlDe		;compare rcvPtr-start of next track
	jnc	trkLoop		;another track is present

; All the buffered tracks have been written. Move any bytes left over
;    from the xmodem receive to the start of trkbuf. Adjust rcvPtr
;    to the end of that data which is where reception of the next
;    packet will begin.

	call	subHlDe		;hl=hl-de = left over byte count - PKTLEN
	mov	a,l		;a=left over count - PKTLEN
	adi	PKTLEN		;a=left over byte count
	mov	b,a		;b=left over byte count (bytes to move)
	lxi	h,trkBuf	;hl->start of trkBuf
	jz	mvDone		;no bytes to move, we're done
	
; Copy the leftover data to the start of trkBuf. The next XMODEM receive
;   sequence will start at the end of this copied data instead of at the
;   start of trkBuf.

moveLp	ldax	d		;move from end of trkBuf to start of trkBuf
	mov	m,a
	inx	h		;hl->starting bytes of trackbuf
	inx	d		;de->unwritten bytes from end of trkBuf		
	dcr	b
	jnz	moveLp

mvDone	shld	rcvPtr		;save address where to receive next packet
	mvi	a,ACK		;ACK the last packet or EOT
	call	sndByte
	jmp	mainLp		;go receive more packets

; allDone - The disk is completely written. ACK the final packet (or EOT),
;     display the "transfer complete" message and start the program over.

allDone	mvi	a,ACK		;ACK the final packet or EOT
	call	sndByte
	lxi	h,mDone		;hl->done message
	call	dispMsg
	jmp	getDrv		;start over asking for drive num

;-----------------------------------------------------------------------------
; bufPkts - Receive XMODEM packets until we fill all the track buffer
;   space available. Reception starts at the address pointed to by
;   rcvPtr. Reception is stopped when the last packet exactly
;   fills or "crosses" the end of the last track spot in RAM. rcvPtr is
;   updated on exit to point to the start of the last packet received.
;   The disk write routines use this pointer to know where data ends and
;   then update rcvPtr to start to where to begin receiving new packets.
;-----------------------------------------------------------------------------
bufPkts	call	rcvPkt		;receive a packet
	xchg			;de=current xmodem receive pointer
	cpi	EOT		;EOT received?
	jz	bufDone		;yes, buffering is done
	lhld	bufEnd		;hl=end of buffering space
	call	cmpDeHl		;compare current-end	
	jnc	bufDone		;past or at end, buffering is done
	mvi	a,ACK		;otherwise, ACK the packet
	call	sndByte
	xchg			;put xmodem rcv pointer back in HL
	jmp	bufPkts		;buffer some more

; bufDone - no more room for packets. Update rcvPtr to point to the 
;   start of the last packet received so the disk write routines know
;   where data ends.

bufDone	xchg			;hl=current xmodem receive pointer
	lxi	d,-PKTLEN
	dad	d		;hl=hl-PKTLEN = start of last rcv'd packet
	shld	rcvPtr		;save use by write tracks
	ret

;-----------------------------------------------------------------------------
; rcvPkt - receive an xmodem format 128 byte packet. HL points to the 128 byte
;    buffer to receive. HL is updated by 128 bytes after each succuessful
;    reception of a new 128 byte packet.
;-----------------------------------------------------------------------------
nakPkt	pop	h		;get HL back
	mvi	a,NAK
	call	purgSio		;purge receive for 1s then transmit NAK

;wait for SOH or EOT

rcvPkt	push	h		;save HL for retries
waitSoh	call	chkQuit		;check for user abort
	mvi	a,3		;3 second timeout for soh
	call	rcvByte		;receive character with timeout
	jz	nakPkt		;timeout
	cpi	SOH		;SOH received?
	jz	haveSoh
	cpi	EOT		;EOT to say we're done?
	jnz	waitSoh		;no, keep looking for SOH
	pop	h		;undo the entry push
	ret			;return with EOT

;  Have SOH, receive block number and not block number

haveSoh	mvi	a,1		;one second timeout once inside a packet
	call	rcvByte		;get the block number
	jz	nakPkt		;timeout, NAK and start over
	sta	rcvBlk		;save the received block number
	mvi	a,1		;one second timeout
	call	rcvByte		;get not block number
	jz	nakPkt		;timeout, NAK and start over
	sta	rcvNBlk		;save not block number

;  Receive the 128 byte block

	mvi	e,0		;init checksum
	mvi	d,pktLen	;d is byte counter
pktLoop	mvi	a,1		;one second timeout
	call	rcvByte		;get next data byte
	jz	nakPkt		;timeout
	mov	m,a		;store the character
	inx	h		;point to next byte
	add	e		;update the checksum
	mov	e,a
	dcr	d		;decrement bytes remaining
	jnz	pktLoop

;  Verify the checksum

	mvi	a,1		;one second timeout
	call	rcvByte		;get the checksum
	jz	nakPkt		;timeout
	cmp	e		;checksum match?
	jnz	nakPkt		;no, packet error

;  Checksum good. Verify block numbers

	lda	rcvNBlk		;verify rcvBlk = not (rcvNBlk)
	cma			;A should = block number now
	mov	b,a		;save in b
	lda	rcvBlk
	cmp	b		;compare rcvBlk = not(rcvNBlk)?
	jnz	nakPkt		;no, error
	lda	blkNum		;compare rcvBlk = expected blkNum
	cmp	b
	jnz	nakPkt		;nak if not the same (also nak's re-send)
	inr	a		;increment expected block number
	sta	blkNum
	pop	b		;get HL off stack, but don't clobber HL
	xra	a		;return a zero
	ret

;-----------------------------------------------------------------------------
; wrtTrk - write and verify NUMSEC sectors to the current track in trkBuf
;   as pointed to by trkPtr. After the track is written, trkPtr is updated
;   by the length of a track to point to the next track buffer. This
;   saved value is also returned in HL.
;-----------------------------------------------------------------------------
wrtTrk	lxi	h,trkNum	;get desired track from trkNum	
	mov	l,m		;and put into l
	call	dSeek		;seek to the track
	call	dChkWP		;check write protect
	mvi	a,WRTRIES	;init write retry counter
	sta	wrRetry
rtryWrt	mvi	d,NUMSEC	;d=count of sectors to write

; wrtLoop - write a full track starting with any sector

wrtLoop	call	dNxtSec		;wait for next (any) sector sync
	lhld	trkPtr		;hl->start of current track buffer
	dad	b		;bc has offset of sector within track
	call	dWrite		;write the sector
	dcr	d		;decrement sector count
	jnz	wrtLoop		;loop until all sectors written

; Verify the track just written

	call	dNxtSec		;force a 1 sector delay for trim erase
	mvi	d,NUMSEC	;d=count of sectors to write
vfyLoop	call	chkQuit		;check for ctrl-c
	call	dNxtSec		;wait for next (any) sector sync
	lhld	trkPtr		;hl->start of current track buffer
	dad	b		;bc has offset of sector within track
	call	dVerify		;verify the sector
	jnz	vfyRtry		;error, go to retry logic
vfyNext	dcr	d		;decrement sector count
	jnz	vfyLoop		;loop until all sectors verified

; Track verified, increment trkPtr to memory location for next track
;    and exit.

	lhld	trkPtr		;hl=current track pointer
	lxi	d,TRKLEN	;de=bytes in a track
	dad	d		;hl=start of next track in trkBuf
	shld	trkPtr
	ret

; vfyRtry - verify failed, retry reads followed by a re-write
;   of the track in needed.

vfyRtry	mvi	a,RDTRIES	;init retry counter
	sta	rdRetry
retryLp	call	chkQuit		;check for ctrl-c
	call	dWtSec		;wait for sector specified in e
	lhld	trkPtr		;hl->start of current track buffer
	dad	b		;bc has offset of sector within track
	call	dVerify		;verify the sector
	jz	vfyNext		;success, go verify next sector

; Re-verify failed. Decrement retry count and try again if not zero. Once
;   retry counter expires, do another write.

	lxi	h,rdRetry	;decrement the read retry counter
	dcr	m
	jnz	retryLp		;try again

; read re-tries expired, decrement the write retry count and re-write
;    if not expired

	lxi	h,wrRetry	;decrement the write retry counter
	dcr	m
	jnz	rtryWrt		;retry starting with the write
				;fall through to disk fail 
;-----------------------------------------------------------------------------
; Disk write failure. Display the track and sector with the error. Restart
;    the program.
;-----------------------------------------------------------------------------
	lxi	h,errTrk	;hl->where to put ascii decimal
	lda	trkNum		;a=track with error on it
	call	bin2dec		;track to ascii

	lxi	h,errSec	;hl->where to put ascii sector
	mov	a,e		;a=sector where error occured
	call	bin2dec

	lxi	h,mDskErr	;display the error message
	call	dispMsg
	lxi	sp,ourStk	;initialize stack pointer
	jmp	getDrv		;start over asking for drive num

;-----------------------------------------------------------------------------
; dispMsg - display the null-terminated message passed in hl on the
;    console device. Clobbers b, hl
;-----------------------------------------------------------------------------
dispMsg	mov	a,m		;get the next message byte
	ora	a		;null terminates
	rz
	mov	b,a		;conOut wants character in b
	call	conOut
	inx	h		;move to next byte
	jmp	dispMsg

;-----------------------------------------------------------------------------
; rcvCon - Receive a character from the console device, echo it, then
;   wait for a CR. Exits program if Ctrl-c typed. Returns with invalid
;   character (null) if BS or DEL pressed after 1st character
;   Returns character in a, clobbers b.
;-----------------------------------------------------------------------------
rcvCon	call	conIn		;check for input
	jz	rcvCon		;nothing
	ani	7fh
	cpi	CTRLC		;abort requested?
	jz	pgmExit		;yes
	cpi	CR		;return pressed?
	rz			;yes, don't echo it
	mov	b,a		;conOut needs character in b
	call	conOut		;echo it

; Wait for CR, then return 1st character typed

rcvCr	call	conIn		;check for input
	jz	rcvCr		;nothing
	ani	7fh
	cpi	CTRLC		;abort requested?
	jz	pgmExit		;yes
	cpi	DEL		;delete
	rz			;yes, return DEL character
	cpi	BS		;backspace?
	rz			;yes, return BS character
	cpi	CR		;return pressed?
	jnz	rcvCr		;no, keep waiting
	mov	a,b		;return 1st character typed
	ret

;-----------------------------------------------------------------------------
; purgSio - Wait for 1 second of idle time on receive line, then transmit the
;	character passed in A (usually ACK or NAK). Clobbers b
;-----------------------------------------------------------------------------
purgSio	push	a
purge	mvi	a,1		;1 second timeout
	call	rcvByte		;wait for 1 second without activity
	jnz	purge
	pop	a		;get back the character to send
				;fall through to sndByte
;-----------------------------------------------------------------------------
; sndByte - send the byte in a through the specified transfer port. 
;     Clobbers b. (assuming serOut clobbers only a).
;-----------------------------------------------------------------------------
sndByte	mov	b,a		;b=byte to transmit
	jmp	serOut		;send the character

;-----------------------------------------------------------------------------
; rcvByte - Receive a byte from the specified transfer port. A wait timeout
;     in seconds is specified in a. If a timeout occurs, zero is returned in
;     a and the zero flag is true. Otherwise, the character is returned in a 
;     (could be zero) and the zero flag is false. The loop here is 51 cycles
;     plus the time serIn takes to return no character. ONESEC should be set
;     appropriately. Clobbers a, b and c.
;-----------------------------------------------------------------------------
rcvByte	push	d		;save d, e
	mov	d,a		;save timeout in d

initSec	lxi	b,ONESEC	;bc=cycles through this loop for 1s
rcvWait	call	serIn		;(17+29) look for a byte
	jnz	haveChr		;(10) byte received
	dcx	b		;(5) otherwise, decrement timer
	mov	a,b		;(5) one second expire?
	ora	c		;(4)
	jnz	rcvWait		;(10) no, keep waiting

; one second timeout has occured. Decrement the seconds counter.

	dcr	d		;decrement seconds counter
	jnz	initSec		;initialize for another 1 second count
haveChr	pop	d		;restore d, e
	ret

;--------------------------------------------------------------
; bin2dec - Binary byte in A to 2 ASCII digits at (HL)
;   HL is preserved
;--------------------------------------------------------------
bin2dec	mvi	m,' '		;assume zero supression
	sui	10		;value less than 10?
	jc	do1s		;yes, leading blank
	mvi	m,'1'		;have one ten already

loop10	sui	10		;count 10s
	jc	do1s		;done with 10s, do 1s
	inr	m
	jmp	loop10

do1s	adi	'0'+10		;form ASCII 1s digit
	inx	h		;move to 1s position
	mov	m,a
	dcx	h		;restore hl
	ret

;--------------------------------------------------------------
; chkQuit - check for the user to request abort (ctrl-c). If
;    a character is present on the console port, read it and
;    see if ctrl-c. Clobbers A
;--------------------------------------------------------------
chkQuit	call	conIn		;check for console input
	rz
	ani	7fh
	cpi	CTRLC		;abort requested?
	rnz			;no

; Ctrl-C typed while program is running. Return to drive prompt.

	lxi	sp,ourStk	;initialize stack pointer
	jmp	getDrv		;start over asking for drive num

;--------------------------------------------------------------
; pgmExit - Exit to CP/M or to the monitor ROM based on the
;    CP/M flag
;--------------------------------------------------------------
pgmExit	lda	cpmFlag		;running under CP/M?
	ora	a
	jnz	cpmExit		;yes

; Exit to ROM monitor

	lxi	h,mExit		;display "exiting" message
	call	dispMsg
	jmp	MONITOR		;jump to ROM monitor entry point

; CP/M exit. If boot drive was used, prompt user to insert CP/M disk

cpmExit	lda	drvNum		;boot drive used?
	sui	MINDRV
	jnz	noDisk		;not 1, disk prompt not needed
	lxi	h,mCpm		;display "insert cp/m disk"	
	call	dispMsg
	call	rcvCon		;wait for a character
noDisk	lxi	h,mExit		;display "exiting" message
	call	dispMsg
	jmp	CPMBOOT		;reboot CP/M

;--------------------------------------------------------------
; chkCpm - check if running under CP/M. CP/M flag is set true
;   (non-zero) if yes, cleared otherwise.
;--------------------------------------------------------------
; First, initialize entries for stand-alone

chkCpm	xra	a
	sta	cpmFlag		;clear CP/M flag
	mvi	a,MINDRV+'0'	;ascii for minimum drive number
	sta	mDrvMin		;store in the drive prompt message
	sta	baseDrv		;ascii 1st drive - baseDrv = 0
	mvi	a,MAXDRV+'0'	;ascii for max drive number
	sta	mDrvMax

; Determine if we're under CP/M or standalone. CP/M is assumed if
;   a jump instruction is present at the CP/M warm start location (0)
;   and five more jumps (e.g., a jump table) is present at the
;   jump-to destination.
		
	lda	WBOOT		;see if jump instruction present for CP/M
	cpi	JMPINST
	rnz			;no, not CP/M

; A jump instruction is present at the CP/M warm boot location (0),
;   now see if that jump points to five more jumps. If so, assume CP/M

	lxi	h,WBOOT+1	;point to lsb of jump address
	mov	e,m		;e=low byte of jump
	inx	h
	mov	d,m		;de=destination of jump
	mvi	b,5		;look for 5 more jumps (a jump table)
jmpTest	ldax	d		;a=opcode at jump destination
	sui	JMPINST		;another jump present?
	rnz			;no, not CP/M
	inx	d		;move to next jump
	inx	d
	inx	d
	dcr	b
	jnz	jmpTest
	dcr	a		;a=0ffh
	sta	cpmFlag		;CP/M flag to non-zero = true

; We're running under CP/M. Change drive prompt message to show drive
;    letters instead of drive numbers and change baseDrv to convert
;    an 'A' to the base drive number (MINDRV).

	mvi	a,'A'		;'A' in drive message instead of number
	sta	mDrvMin
	adi	MAXDRV-MINDRV	;max drive letter
	sta	mDrvMax
	mvi	a,'a'		;ascii 1st drive - baseDrv = 0
	sta	baseDrv
	ret

;------------------------------------------------------------------
; sizeRam - determine how much RAM we have for buffering tracks.
;   Sets the bufEnd variable which points to end address of 
;   the last possible track buffer + 1
;------------------------------------------------------------------
sizeRam	lxi	h,(trkBuf+0ffh) AND 0ff00h   ;next 256 byte boundary
ramLoop	mov	a,m		;a=current RAM content
	inr	m		;change RAM
	cmp	m		;did RAM change?
	mov	m,a		;restore RAM
	jz	ramEnd		;end of RAM found
	inr	h		;next page
	jnz	ramLoop

; ramEnd - end of RAM found. Subtract 256 bytes from this to make room
;   for xmodem packet overflow at the end. Determine the end address + 1
;   of the last track buffer that will fit in RAM. Store in bufEnd

ramEnd	xchg			;de=end of RAM + 1
	mvi	a,-((TRKLEN SHR 8) + 1) AND 0ffh
	cmp	d		;force de < (10000h - TRKLEN)
	jnc	topOk
	mov	d,a		;limit max address
topOk	dcr	d		;subtract 256 bytes from end of RAM
	lxi	h,trkBuf	;hl=start of track buffer
	lxi	b,TRKLEN	;bc=length of track in bytes

; Loop increasing hl by TRKLEN until hl > end of RAM.

bfEndLp	dad	b		;hl=hl+track length
	call	cmpHlDe		;compare hl-de
	jc	bfEndLp		;still more room, keep going

; Subtract one track length from hl, this will be the end address + 1 of
;   the the last track buffer that will fit in RAM

	lxi	b,-TRKLEN	;subtract one track length
	dad	b		;hl = end address of last track + 1
	shld	bufEnd		;save as bufEnd
	ret

;--------------------------------------------------------------------
; cmHlDe - compare HL-DE. Carry set if HL<DE, carry clear if HL>=DE
;--------------------------------------------------------------------
cmpHlDe	mov	a,l		;compare HL-DE, do lsbs first
	sub	e
	mov	a,h		;do msbs
	sbb	d
	ret			;carry set HL<DE, clear HL>=DE

;--------------------------------------------------------------------
; cmDeHl - compare DE-HL. Carry set if DE<HL, carry clear if DE>=HL
;--------------------------------------------------------------------
cmpDeHl	mov	a,e		;compare DE-HL, do lsbs first
	sub	l
	mov	a,d		;do msbs
	sbb	h
	ret			;carry set DE<HL, clear DE>=HL

;--------------------------------------------------------------------
; subHlDe - HL=HL-DE
;--------------------------------------------------------------------
subHlDe	mov	a,l		;subtract HL-DE, do lsbs first
	sub	e
	mov	l,a		;lsb result in l
	mov	a,h		;do msbs
	sbb	d
	mov	h,a		;msb result in h	
	ret
;-----------------------------------------------------------------------------
;   Data Area
;-----------------------------------------------------------------------------
mWelcom	db	cr,lf,lf
	db	'===== PC to Floppy Image Transfer, Version 1.4 ====='
	db	cr,lf,lf
	db	'This program writes a Micropolis floppy from a disk image'
	db	cr,lf
	db	'received through a serial port using XMODEM.',0

mDrive	db	cr,lf,lf,'Insert and specify destination drive ('
mDrvMin	db	'x-'
mDrvMax	db	'x) or X to exit: ',0

mPort	db	cr,lf,lf
	db	'Specify the serial port to use for file transfer',cr,lf
	db	'  1) Bitstreamer II port A (2/3)',cr,lf
	db	'  2) Bitstreamer II port B or ZCB port A (4/5)',cr,lf
	db	'  3) Bitstreamer II port C (6/7)',cr,lf
	db	'Enter port or X to exit: ',0

mStart	db	cr,lf,lf
	db	'Start XMODEM send now...',0

mDone	db	cr,lf,lf,'Creation of new disk successful!',cr,lf,0

mNoTrk0	db	cr,lf,lf,'Seek to track 0 failed',cr,lf,0

mStkTk0	db	cr,lf,lf,'Drive stuck on track 0',cr,lf,0

mNotRdy	db	cr,lf,lf,'Drive not ready',cr,lf,0

mDskErr	db	cr,lf,lf,'Write failure on track '
errTrk	db	'xx, sector'
errSec	db	'xx. Disk creation aborted.',cr,lf,0

mWrtPrt	db	cr,lf,lf,'Disk is write protected',cr,lf,0

mExit	db	cr,lf,lf,'Exiting...',cr,lf,0

mCpm	db	cr,lf,lf
	db	'Insert CP/M disk into drive A, then press Return...',0



;****************************************************************************
;
;  Hardware specific console and serial I/O routines. 
;     The following four  routines must be written to provide a common
;     interface to the hardware on which this program is running. The
;     port number specified for serIn and serOut matches the port number
;     input from the operator via the port menu.
;
;****************************************************************************

; The rcvByte subroutine above times a one second timeout with a code
;    loop that calls the hardware specific serIn routine below. ONESEC
;    must be set based on processor speed and the number of cycles in 
;    the serIn call + 51 cycles for the rcvByte code. 

ONESEC	equ	50000		;rcvByte loop count for 1 second (4MHz)

; VG Monitor I/O equates

KEYTST	equ	VGMON+3		;test keyboard in VG ROM monitor
KEYDATA	equ	VGMON+6		;input from keyboard in VG ROM monitor
CRT	equ	VGMON+9		;output to screen in VG ROM monitor

; Serial port equates for 8251 on Bitstreamer II and ZCB

PORTDR	equ	2		;port A is at 2/3
PORTSR	equ	3
XMTMASK	equ	1		;mask to isolate transmit ready bit
RCVMASK	equ	2		;mask to isolate receive ready bit

;----------------------------------------------------------------------------
; conIn - input character from console
;    inputs:
;    outputs: z true if no character present
;	      z false if character returned in a
;    clobbers none
;----------------------------------------------------------------------------
conIn	call	KEYTST		;call ROM monitor to test for console input
	rz			;return zero true if none
	jmp	KEYDATA		;get character typed from ROM monitor

;----------------------------------------------------------------------------
; conOut - output character to console
;    inputs: b = character to send
;    clobbers none
;----------------------------------------------------------------------------
conOut	mov	a,b		;monitor expects character in a
	jmp	CRT		;send/display it

;----------------------------------------------------------------------------
; serIn - input character from transfer port. The port addresses below
;    are modified based on the port number selected by the operator.
;
;    outputs: z true if no character present
;	      z false if character returned in a
;    clobbers none
;    29 cycles when not returning a character
;-----------------------------------------------------------------------------
serIn	in	PORTSR		;a=port status register
	ani	RCVMASK		;isolate receive ready bit
	rz			;nothing present
siData	in	PORTDR		;a=character from serial port
	ret			

;-----------------------------------------------------------------------------
; Hardware specific I/O
; serOut - output character to port specified in a. The port addresses
;    below are modified based on the port number selected by the operator.
;
;    inputs: a = port to transmit through
;	     b = character to send
;    clobbers none
;-----------------------------------------------------------------------------
serOut	in	PORTSR		;a=port status register
	ani	XMTMASK		;isolate transmit ready bit
	jz	serOut		;not ready

	mov	a,b		;a=character to transmit
soData	out	PORTDR		;transmit the character
	ret

;****************************************************************************
;
;  DISK DRIVER FOR MICROPOLIS FLEXIBLE DISK SUBSYSTEM
;
;  Created for PC2Flop and Flop2PC by Mike Douglas 11/2014 from
;  the Micropolis driver code (COPYRIGHT MICROPOLIS CORPORATION 8 JUNE 1977)
;
;  Original code is in all caps. New code is in lower case.
;
;****************************************************************************

;***************************************
;	REGISTER DEFINITIONS AND
;	FLAG EQUATES FOR MICROPOLIS
;	FLEXIBLE DISK CONTROLLER B
;***************************************

BPROM 	EQU 	0F800H
FDCBASE	EQU 	BPROM+0200H
SCLEN 	EQU 	270		;sector length including sync and cksum

; FDC STATUS REGISTERS

; Sector register is at FDCBASE
;     0-3 SECTOR COUNT
;	4 SPARE
;	5 SPARE
;	6 SCTR INTERRUPT FLAG
;	7 SECTOR FLAG
;
;	FLAG BITS

SIFLG	EQU 	040H
SFLG	EQU 	080H
DTMR	EQU 	020H

; Status register is at FDCBASE+1
;     0-1 UNIT ADDRESS
;	2 UNIT SELECTED (LOW TRUE)
;	3 TRACK 0
;	4 WRITE PROTECT
;	5 DISK READY
;	6 PINTE
;	7 TRANSFER FLAG
;
;	FLAG BITS

TFLG	EQU 	80H
INTE	EQU 	40H
RDY	EQU 	20H
WPT	EQU 	10H
TK0	EQU 	08H
USLT	EQU 	04H

; Command register at FDCBASE (and again at FDCBASE+1)
;	0-1 COMMAND MODIFIER
;	5-7 COMMAND
;
;	COMMANDS

SLUN	EQU 	020H		;SELECT UNIT
;  MODIFIER CONTAINS UNIT ADDRESS

SINT	EQU 	040H		;SET INTERRUPT
;  MODIFIER = l ENABLE INTERRUPT
;  	      0 DISABLE INTERRUPT

STEP	EQU 	060H		;STEP CARRIAGE
;  MODIFIER = 00 STEP OUT
;  	      01 STEP IN

WTCMD	EQU 	080H		;ENABLE WRITE
;  NO MODIFIER USED

RESET	EQU 	0A0H		;RESET CONTROLLER
;  NO MODIFIER USED

;-------------------------------------------------------------
; dWrite - Write a sector on current track
; On Entry:
;    Drive is selected, motor is running and sector
;        sync was just previously detected
;    hl->buffer address
; On Exit:
;   clobbers b,c,h,l
;-------------------------------------------------------------
dWrite	push	d		;save de
	xchg			;de->buffer
	lxi	h,FDCBASE+1	;hl->FDC status register

; ENABLE WRITE AND WAIT FOR TRANSFER FLAG

	MVI 	M,WTCMD		;command register at offset of 0 and 1
dWrWait	ORA 	M
	JP 	dWrWait

; Write 270 bytes from memory including the sync byte and checksum.
;    If wrong in the memory buffer, they'll be wrong on disk.

	INX 	H		;hl->FDC data register
	XCHG			;de->FDC data register, hl->buffer
	mvi	c,SCLEN/2	;transferring 270 bytes

; Write loop

dWrLoop	MOV 	A,M		;GET BYTE FROM MEM
	STAX 	D		;WRITE TO DISK
	INX 	H		;NEXT BYTE
	MOV 	A,M		;-ETC-
	STAX 	D
	INX 	H
	DCR 	C
	JNZ 	dWrLoop
	pop	d		;restore de
	RET

;-------------------------------------------------------------
; dChkWP - check if disk is write protected.
; On Entry:
;    drive already selected
; On Exit:
;    returns if OK to write, otherwise, restarts the program
;    asking for the disk prompt
; clobbers h,l
;-------------------------------------------------------------
dChkWP	lxi	h,FDCBASE+1	;hl->FDC status register
	mov	a,m		;check for write protect
	ani	WPT
	rz			;return if not protected

; Protected, display message and restore state to start
;    of program

	lxi	h,mWrtPrt	;otherwise, display error message
	call	dispMsg		;display the error
	lxi	sp,ourStk	;re-init stack pointer
	jmp	getDrv		;go back to drive prompt

;-------------------------------------------------------------
; dRead - Read sector on current track. Copies sync byte,
;    266 byte data section, and checksum byte.
; On Entry:
;    Drive is selected, motor is running and sector
;        sync was just previously detected
;    hl->sector buffer
;    e = sector number (used for compare)
; On Exit:
;    Success = zero true (valid checksum, track, sector)
;    clobbers b,c,h,l
;-------------------------------------------------------------
; First, wait for transfer ready flag (sector data available)

dRead	push	d		;save de
	xchg			;de->buffer
	lxi	h,FDCBASE+1	;hl->FDC status register
	xra	a		;a=0

dRdWait	ora	m		;wait for transfer ready flag in msb
	jp	dRdWait

; sector data ready - pull off sync byte
		
	xchg			;hl->buffer, de->FDC status register
	inx	d		;de->FDC data register
	ldax	d		;read and save sync byte
	mov	m,a
	inx	h
	shld	hdrPtr		;pointer to sector header (track #, sec #)

; dRdLoop - Read loop. Read 268 bytes of sector content two bytes
;    at a time computing checksum in B. Carry started clear with
;    ora instruction at dRdWait.

	lxi	b,(SCLEN-2)/2	;b=0 checksum, c=268 bytes/2
dRdLoop	LDAX 	D		;READ FROM DISK
	MOV 	M,A		;MOVE TO BUFFER
	INX 	H		;NEXT LOC
	ADC 	B		;ADD TO CHECKSUM
	MOV 	B,A		;AND SAVE

	LDAX 	D		;NEXT READ
	MOV 	M,A		;-ETC-
	INX 	H
	ADC 	B
	MOV 	B,A

	DCR 	C		;END OF DATA?
	JNZ 	dRdLoop		;NO-LOOP

; END OF DATA-READ CHECKSUM and compare

	LDAX 	D		;load checksum from disk
	mov	m,a		;store in read buffer
	inx	h
	CMP 	B		;COMPARE WITH computed
	POP	D		;RESTORE DE	
	RNZ			;RETURN IF ERROR

; CHECKSUM OK - verify track and sector

	lhld	hdrPtr		;hl->track number read (sector header)
	lda	trkNum		;a=expected track number
	cmp	m		;right track?
	rnz			;no, exit with error
	inx	h		;hl->sector number read
	mov	a,m		;a=sector number read
	cmp	e		;right sector?
	ret			;return with status

;-------------------------------------------------------------
; dVerify - Verify sector on current track. Compares all 266
;    bytes of the sector plus sync and checksum.
; On Entry:
;    Drive is selected, motor is running and sector
;        sync was just previously detected
;    hl->sector buffer to compare against
; On Exit:
;    Success = zero true (valid compare)
;    clobbers b,c,h,l
;-------------------------------------------------------------
; First, wait for transfer ready flag (sector data available)

dVerify	push	d		;save de
	xchg			;de->buffer
	lxi	h,FDCBASE+1	;hl->FDC status register
	xra	a		;a=0

dVfWait	ora	m		;wait for transfer ready flag in msb
	jp	dVfWait

; Sector data ready, prepare to compare bytes
		
	xchg			;hl->buffer, de->FDC status register
	inx	d		;de->FDC data register
	mvi	c,SCLEN/2	;c=270 bytes (270/2)

; dVfLoop - Verify loop. Read sector content two bytes at a time
;    comparing to buffer.

dVfLoop	ldax	d		;a=byte from disk
	cmp	m		;match buffer?
	jnz	dVfErr		;no, have an error
	inx	h		;move to next byte

	ldax	d		;a=byte from disk
	cmp	m		;match buffer?
	jnz	dVfErr		;no, have an error
	inx	h		;move to next byte

	dcr	c		;all bytes done?
	jnz	dVfLoop		;no, keep going

; All bytes verified including sync and checksum bytes

dVfErr	pop	d		;restore de
	ret			;return with status

;-------------------------------------------------------------
; dWtSec - Wait for specified sector.
; On Entry:
;    Drive is selected, motor is running
;    e = desired sector number
; On Exit:
;    drive is at proper sector
;    e = sector number
;    bc = byte offset of this sector in a track
;    clobbers hl
;-------------------------------------------------------------
dWtSec 	lxi	h,FDCBASE	;hl->sector register
dWtSec1	mov	a,m		;a=sector register
	ora	a		;test for msb to be set
	jp 	dWtSec1

; have sector pulse. See if this is the right sector. If so,
;   return the byte offset of the sector within a track in bc

	ani	0fh		;get sector number alone
	cmp	e		;right sector?
	jnz	dWtSec1		;no

	mvi	h,(mult275 SHR 8)  ;h=msb of "multiply by 275" table
	rlc			;sector*2 (2 bytes per table entry)
	mov	l,a		;hl->sec*275 (table on 256 byte boundary)
	mov	c,m		;get bc=sec*275
	inx	h
	mov	b,m		;bc=byte offset of sector within a track
	ret

;-------------------------------------------------------------
; dNxtSec - Wait for next (any) sector.
; On Entry:
;    Drive is selected, motor is running
; On Exit:
;    drive is at proper sector
;    e = sector number
;    bc = byte offset of this sector in a track
;    clobbers hl
;-------------------------------------------------------------
dNxtSec	lxi	h,FDCBASE	;hl->sector register
dWtSec2	mov	a,m		;a=sector register
	ora	a		;test for msb to be set
	jp 	dWtSec2

; have sector pulse, return the sector number in e and the
;   byte offset of the sector within a track in bc

	ani	0fh		;get sector number alone
	mov	e,a		;return sector number in e
	mvi	h,(mult275 SHR 8)  ;h=msb of "multiply by 275" table
	rlc			;sector*2 (2 bytes per table entry)
	mov	l,a		;hl->sec*275 (table on 256 byte boundary)
	mov	c,m		;form bc=sec*275
	inx	h
	mov	b,m		;bc=byte offset of sector within a track
	ret

;------------------------------------------------------------------
; mult275 - table to multiply byte 0-15 by 275. This table is
;    on a 256 byte boundary to speed up its use.
;------------------------------------------------------------------
	org	($+255) and 0ff00h
mult275	dw	00*275,01*275,02*275,03*275,04*275,05*275,06*275,07*275
	dw	08*275,09*275,10*275,11*275,12*275,13*275,14*275,15*275	
	

;-------------------------------------------------------------
; dSeek - Seek Track. The motor timeout is restarted 
;    as a result of this call.
; On Entry:
;    curTrk = current track, FFh means we don't know
;    l = desired track
; On Exit:
;    curTrk = current track
; trashes all registers
;-------------------------------------------------------------
dSeek	CALL 	SLCT		;ENSURE DRIVE SELECTED
	mov	c,l		;leave track in c from here on
	lxi	h,curTrk	;hl->current track
	mvi	a,0ffh		;has head position been initialized?
	cmp	m
	jnz	SEEK1		;yes	
	CALL 	dRestor		;no, restore to track 0
SEEK1	mov	a,c		;a=desired track
	SUB 	M		;ALREADY AT TRACK?
	rz 			;yes, exit

; NOT AT TRACK — ISSUE THE
;    APPROPRIATE NUMBER OF STEPS TO
;    MOVE TO THE DESIRED TRACK

	mov	m,c		;update curTrk with new position
	JM 	SEKOUT
SEKIN	CALL 	STEPIN
	DCR 	A
	JNZ 	SEKIN
	JMP 	SEEKR1

SEKOUT	CALL 	STPOUT
	INR 	A
	JNZ 	SEKOUT

SEEKR1	CALL 	SETTLE 		;WAIT HEAD SETTLE
	RET

; STEP POSITIONER IN 1 TRACK

STEPIN	PUSH 	PSW
	PUSH	H
	lxi	h,FDCBASE	;STEP IN ONE TRK
	MVI 	M,STEP+1
	LXI 	D,30		;WAIT STEP TIME
	CALL	TIMER
	POP	H
	POP 	PSW
	RET

; STEP POSITIONER OUT 1 TRACK

STPOUT	PUSH 	PSW
	PUSH	H
	lxi	h,FDCBASE	;STEP IN ONE TRK
	MVI 	M,STEP 		;STEP OUT ONE TRK
	LXI 	D,30		;WAIT STEP TIME
	CALL	TIMER
	POP	H
	POP 	PSW
	RET

; WAIT HEAD SETTLE TIME

SETTLE	LXI 	D,10 		;10 MILLISECONDS
	CALL 	TIMER
	RET

;-------------------------------------------------------------
; dRestor - Restore to track 0. Selects the drive
;    and starts the motor if needed.
; On Exit:
;   Z set and curTrk=0 if track 0 found
; trashes psw,d,e
;-------------------------------------------------------------
dRestor	PUSH	H		;save hl and bc		
	PUSH 	B
	lxi	h,curTrk	;init current track to "bad"
	MVI 	M,0FFH	 	;PRESET TO BAD TRK
	CALL 	RESTR1 		;RESTORE TO TK 0
	MVI 	M,0		;SET TRACK=0
	POP	B
	POP 	H
	RET

; RESTR1 - RESTORE TO TK 0

RESTR1 	PUSH 	H
	CALL 	SLCT		;ENSURE UNIT selected and read
	lxi	h,FDCBASE+1	;hl->FDC status register
	MOV 	A,M		;ALREADY AT track zero?
	ANI 	TK0
	JZ 	REST3		;NO - PRESS ON

; ALREADY AT TRACK 0 - STEP
;    IN 8 TIMES THEN RESTORE
;    TO ENSURE GOOD POSITION

	MVI 	A,8
REST2	CALL 	STEPIN 		;STEP IN 8
	DCR 	A		;TRACKS
	JNZ 	REST2
	CALL 	SETTLE 		;WAIT SETTLE TIME

; STEP OUT UNTIL TRACK 0 SWITCH
;    IS ACTUATED OR UNTIL 85 STEPS
;    HAVE BEEN ISSUED SO THAT WE
;    DONT BANG AGAINST THE STOP
;    FOREVER IF TK0 SWITCH IS
;    BROKEN

REST3	MVI	C,85		;LOAD MAX STEPCNT
REST3A	MOV	A,M		;TRACK 0?
	ANI	TK0
	JNZ	REST4		;YES- PRESS ON
	CALL	STPOUT		;STEP OUT ONE TK
	DCR	C		;MAX STEPS ?
	JNZ 	REST3A 		;NO - TRY AGAIN

; MAXIMUM NUMBER OF STEPS HAVE
;    BEEN ISSUED - ERROR ABORT

	lxi	h,mNoTrk0
	call	dispMsg
	lxi	sp,ourStk	;initialize stack pointer
	jmp	getDrv		;start over asking for drive num

; FOUND TRACK 0 - WAIT
;    SETTLE TIME THEN EXIT

REST4	CALL 	SETTLE		;WAIT HEAD SETTLE
	POP 	H
	RET

;-------------------------------------------------------------
; SELECT DRIVE specified in drvNum
;-------------------------------------------------------------
SLCT 	PUSH 	D
	PUSH 	B
	PUSH 	H
	lxi	h,FDCBASE+1	;hl->FDC status register
	lda	drvNum		;a=disk number
	MOV 	B,A		;AND SAVE
	MOV 	A,M		;read selected unit from controller
	MOV 	C,A		;SAVE in c
	ANI 	7		;MASK selected device number
	XRA 	B		;DESIRED UNIT PREV

; NOTE-THIS TEST WILL FAIL IF CONTROLLER IS NOT PLUGGED IN

	MOV 	A,C		;SELECTED?
	JZ 	SL010		;YES-CHECK RDY
	MOV 	A,B		;GET UNIT ADDRESS
	ORI 	SLUN		;BUILD COMMAND
	MOV 	M,A		;OUTPUT COMMAND
				;WAIT 750 MSEC (up from 250ms) FOR
	LXI 	D,750		;SECTOR CNTR TO
	CALL 	TIMER		;GET IN SYNC
	MOV 	A,M		;GET STATUS
	ANI 	7		;SELECTED NOW?
	XRA 	B
	MOV 	A,M		;GET STATUS AGAIN
	JNZ 	SL020		;ERROR IF NOT SLTD
SL010 	ANI 	RDY		;ENSURE UNIT IS
	XRI 	RDY		;READY
SL020 	POP 	H
	POP 	B
	POP 	D
	RZ			;RETURN IF OK

; DRIVE NOT UP ERROR

	lxi	h,mNotRdy	;drive not ready message
	call	dispMsg
	lxi	sp,ourStk	;initialize stack pointer
	jmp	getDrv		;start over asking for drive num

;-------------------------------------------------------------
; TIMER - 1 MILLISECOND TIMER
;    DE=(DELAY) TIME IN MSEC
;
;    A IS DESTROYED
;-------------------------------------------------------------
TIMER 	PUSH	B
	PUSH 	H
	lxi	h,FDCBASE	;hl->FDC sector register
	MOV 	A,M		;2 or 4 Mhz?
	ANI	DTMR
	MVI	A,96		;1MS @2MHZ
	JNZ	TI005		;IF NOT ZERO, 2MHZ
	RLC			;DOUBLE COUNTER FOR 4MHZ
TI005	MOV	B,A		;SAVE COUNTER IN B
TI010 	MOV 	A,B		;COUNT
	SUI 	1		;DELAY LOOP-1.008
	ORA 	A		;MSEC @500 NSEC
	JNZ 	TI010+1

; 1MSEC EXPIRED - DECREMENT DELAY
;    MULTIPLIER & CHECK FOR DONE

	DCX 	D
	MOV 	A,E
	ORA 	D
	JNZ 	TI010
	POP 	H
	POP 	B
	RET

;-------------------------------------------------------------
; RAM STORAGE REQUIRED FOR DRIVER
;-------------------------------------------------------------
hdrPtr	ds	2		;pointer to sector header (track #, sec #)


;**************************************************************************
; 
;  Data area
;
;**************************************************************************
; disk variables

drvNum	ds	1		;drive number to use
curTrk	ds	1		;current track number drive is on
trkNum	ds	1		;track number to read
trkPtr	ds	2		;pointer into trkBuf (start of next track)
bufEnd	ds	2		;end address + 1 of last track spot in RAM

; retry logic variables

rdRetry	ds	1		;disk read retry counter
wrRetry	ds	1		;disk write retry counter

; xmodem variables

blkNum	ds	1		;current xmodem block number
rcvBlk	ds	1		;block number received
rcvNBlk	ds	1		;"not" block number received
rcvPtr	ds	2		;pointer for start of XMODEM send

; misc variables

cpmFlag	ds	1		;non-zero if running under CP/M
baseDrv	ds	1		;ascii 1st drive - baseDrv = 0
	ds	64		;stack space
ourStk	equ	$

; track buffer runs from here to the end of memory

trkBuf	equ	$

	end

