;		OSBORNE EXECUTIVE - Screen Dump Utility
;
;		- written Dec'84 by Mark Steinbrecher
;			  (with help from Dave Mabry)
;
; This is an RSX to print the screen on an Osborne Executive

rsx	equ	60			; BDOS RSX function call
cr	equ	0dh			; ASCII carriage return character
lf	equ	0ah			; ASCII line feed character
freeram equ	0fb20h			; Address of unused common memory
					; for new conin

serial:
	ds	6			; Initialized by loader
start:
	jmp	begin			; Start of RSX code
next:
	db	0c3h			; Jump instruction
	ds	2			; Initialized by loader
prev:
	ds	2			; Initialized by loader
remove:
	db	0			; Don't remove
nonbank:
	db	0			; Load in all systems
	db	'dump    '		; Name field
loader:
	ds	1			; Loader flag
	ds	2			; Reserved


; Here starts the code that is executed by a call to BDOS with
;  RSX function number in C.

begin:
	mov	a,c			; Get BDOS function number
	cpi	rsx			; Is it for an RSX ?
	jnz	next			; No, pass it on
	ldax	d			; Get RSX function number
	cpi	53			; Is it for this RSX ?
	jnz	next			; No, pass it on
; Must save calling program's stack and use our owm
	lxi	h,0
	dad	sp
	shld	stack
	lxi	sp,stack
; Does calling program want us to remove ourself ?
	mov	h,d
	mov	l,e		;HL point to rsxpb
	inx	h
	inx	h		;Point to param1
	mov	a,m		;Fetch it
	ora	a		;Nonzero means remove
	jz	beg05		;Zero means initialize
	call	next		;In case there is another DUMP RSX
	jmp	die		;Suicide
; Check to see if we are the only DUMP RSX in memory
beg05:
	call	next		;As if we are calling DUMP
	ora	a		;Returns zero if there is another
	jz	die05		;Suicide if another exists
	xchg			;HL point to RSX parameter block
	inx	h
	inx	h		;Point to parameter 1
	mov	a,m		;Get low byte
	ora	a		;Check for zero
	jnz	die		;If not binary 0, then suicide
	inx	h		;Point to trigger passed in
	mov	a,m
	sta	trigger
; At this point, we have to initialize the RSX code to intercept
;  all console input calls.
;  But only if we haven't done it before.
	lda	modified
	ora	a
	jnz	return		;Bypass vector modification if done
	lhld	1		;Get warm boot vector
	lxi	d,7
	dad	d		;Point to console in vector address
	shld	conin$adr	;Save for die also
	push	h		;save temporarily
	mov	a,m		;get low byte of conin vector address
	inx	h		;point to high byte
	mov	h,m		;get high byte of conin vector address
	mov	l,a		;hl reg now has conin address
	shld	old$conin	;store locally
	call	patch		;move patch code into unused BIOS ram
	lxi 	d,freeram 	;new console address to DE
	pop	h		;again point to conin vector in BIOS
	mov	m,e         	;move low byte of unused BIOS ram address
	inx	h		;point to high byte of vector
	mov	m,d           	;conin in vector is now patched !
; Now get the list out routine address in case application program
;  modifies location 1 (warm boot vector).  SuperCalc does this
;  and maybe others.
	lhld	1		;Address of BIOS jump table
	lxi	d,13		;Offset to address of list output
	dad	d
	mov	a,m		;Low byte of list out address
	inx	h
	mov	h,m		;High byte
	mov	l,a
	shld	l$out		;save address
; Indicate that the console in has been modified.
	mvi	a,0ffh		;Set modified flag
	sta	modified
return:
	lhld	stack		;get old stack address
	sphl			;restore
	mvi	a,0		;Indicate success
	ret			;rsx initialization complete

die:
	lda	modified	;Have we modified the BIOS jump table ?
	ora	a
	jz	die05		;No, then just die
	lhld	old$conin	;Get original address of CONIN
	xchg			; to DE
	lhld	conin$adr	;Point to address field in jump table
	mov	m,e		;Restore original jump address
	inx	h
	mov	m,d
die05:
	mvi	a,0ffh		;True flag
	sta	remove		;Flag removal at next warm boot 
	jmp	return

patch:
	mvi	b,length 	;setup loop counter
	lxi 	h,freeram 	;setup address pointer for relocated code
	lxi	d,st$code	;setup address pointer for local code
loop:	ldax	d
	mov	m,a
	inx	h
	inx	d
	dcr	b
	jnz	loop
	ret
;
; The code that follows is relocated to address <freeram> in common
;  memory by <patch:>.  Address <freeram> is patched into the conin
;  vector in the BIOS jump table so that all further console inputs
;  pass through this routine.
st$code:
	in 	0		;get current bank
	push 	psw     	;save temporarily
	mvi	a,41h		;setup bank 1 (TPA bank)
	out	0		;enable TPA
	call	new$conin	;vector to console input patch
	mov	b,a		;move console char. to B temporarily
	pop	psw     	;get old bank back
	out	0		;enable old bank
	mov	a,b		;put console char. back in A
	ret			;ret with console character in A
;
length	equ	$-st$code
;
old:
	lhld	old$conin
	pchl
;
new$conin:
 	push	h
 	lxi	h,0		;Use a local stack
 	dad	sp
 	shld	stack
	lxi	sp,stack
	call	old		;Go get character
 	push	psw		;Save status
	lxi	h,trigger	;Compare with the trigger character
	cmp	m		;Is it the same ?
	cz	doit		;Go dump screen if yes
 	pop	psw		;Else pass it by
 	lhld	stack
 	sphl	
 	pop	h
	ret

doit:	
	lxi	h,0c000h		;point to start of screen ram
	lxi	b,5018h			;set up row and column counters
next$row:
	push	b			;save row and column counts
next$col:
	mov	a,m			;get next char. from screen
	ani	7fh			;strip attribute bit
	cpi	20h			;check for valid ASCII character
	cm	bad
	mov	c,a
	push	h			;save pointer
	push	b
	call	list$out		;print character
	pop	b
	pop	h
	inx	h			;point to next character
	dcr	b			;decrement column counter
	jnz	next$col		;if not zero continue 
	mvi	c,lf			;row finished so print a crlf
	push	h
	call	list$out
	mvi	c,cr
	call	list$out
	pop	h			;recall screen ram pointer
	pop	b			;recall row count & reset col. counter
	dcr	c			;decrement row counter
	rz				;if row count=0, we're done
	lxi	d,30h			;row to row address offset
	dad	d			;not done so point to next row
	jmp	next$row
;
bad:
	mvi	a,20h			;replace nonprintable char. with space
	ret
;
list$out:
	lhld	l$out			;Get address of list out routine
	pchl				;Go do it

modified:
	db	0			;True -> BIOS jump table modified
trigger:
	ds	1			;Place to store trigger character
l$out:
	ds	2			;Place to store address of list out
old$conin:
	ds	2			;Place to store address of old conin
conin$adr:
	ds	2			;Place to store address of jump vector
					; of CONIN in BIOS jump table
	ds	30
stack:
	ds	2			;Place to save original stack
	end