TITLE	"ZMP Overlay for YASBEC/SB-180 and B/P Bios"
;============================================================================
; Overlay to ZMP (Z-Modem Program), for YASBEC Z180 SBC and MicroMint SB-180
;			(B/P Bios Version)
;
;  YASBEC B/P Bios calls used for modem I/O, setup, and breaks.  ZCPR3
;  generic version (overlay uses Z3 termcap for terminal dependant stuff).
;  This is a cut and file to fit version - my apologies for the mess, but
;  hey, it works and we were trying to get something out to you all before
;  the next ice age comes!!!  (Wayne Hortensius)
;
;  This version is locked into ASCI0 on the HD64180/Z-180 chip to insure
;  that routines are speedy enough at higher data rates.  This should not be
;  too much of a hardship since the Baud Rate setup in the generic version
;  was tied into this port anyway.  (Harold Bower)
;
; Name	: ZMO-YBBP.Z80
; Dated	: 2 February 1992
; Author: Harold F. Bower (from ZMO-YB11.Z80, 2 Mar 91, by Wayne Hortensius)
;===========================================================================
; HD64180/Z-180 Ports needed in this overlay

CNTLA0	EQU	00H		; Control Port A ASCI 0
CNTLB0	EQU	02H		; Control Port B ASCI 0
STAT0	EQU	04H		; Status Port, ASCI 0
ODAT0	EQU	06H		; Output Data Port, ASCI 0
IDAT0	EQU	08H		; Input Data Port, ASCI 0

; Set the following two equates to the drive and user area which will
; contain ZMP's .OVR files, .CFG file, .FON file and .HLP file.  Set both
; to zero (null) to locate them on the drive from which ZMP was invoked.

OVRDRV	EQU	'B'		; Drive to find overlay files on ('A'-'P')
OVRUSR	EQU	12		; User area to find files

;------------------------------------------------------------------------------
; User-set variables:

CLKSPD	EQU	9		; Processor clock speed in MHz.  Set to nearest
				;  even MegaHertz
MSPEED	EQU	003CH		; Current Baud Rate Location in Memory: as used
				;  by BYE etc. This MUST be the same as Mspeed
				;  in ZMP.H
USERDEF	EQU	0145H		; origin of this overlay: get this value from
				; the .SYM file produced when ZMP.COM is linked
OVSIZE	EQU	0400H		; max size of this overlay

;------------------------------------------------------------------------------

	ORG	USERDEF

SO	EQU	'N'-'@'
CTRLQ	EQU	11H
CR	EQU	13
LF	EQU	10
BDOS	EQU	5

; Jump table for the overlay: do NOT change this

jump_tab:
	JP	SCRNPR		; screen print
	JP	MRD		; modem read with timeout
	JP	AUXIN		; get a character from modem
	JP	AUXOUT		; send a character to the modem
	JP	AUXOST		; test for tx buffer empty
	JP	AUXIST		; test for character received
	JP	SNDBRK		; send break
	JP	CURSADD		; cursor addressing
	JP	CLS		; clear screen
	JP	INVON		; inverse video on
	JP	INVOFF		; inverse video off
	JP	HIDE		; hide cursor
	JP	SHOW		; show cursor
	JP	SAVECU		; save cursor position
	JP	RESCU		; restore cursor position
	JP	MINT		; service modem interrupt
	JP	INVEC		; initialise interrupt vectors
	JP	DINVEC		; de-initialise interrupt vectors
	JP	MDMERR		; test uart flags for error
	JP	DTRON		; turn DTR on
	JP	DTROFF		; turn DTR OFF
	JP	INIT		; initialise uart
	JP	WAIT		; wait seconds
	JP	MSWAIT		; wait milliseconds
	JP	USERIN		; user-defined entry routine
	JP	USEROUT		; user-defined exit routine
	JP	GETVARS		; get system variables
	JP	SETPORT		; choose one of two (not implemented)

; Spare jumps for compatibility with future versions

	DEFB	0C9H,0,0	; Spare Jump for later use
	DEFB	0C9H,0,0	; Spare Jump for later use
	DEFB	0C9H,0,0	; Spare Jump for later use
	DEFB	0C9H,0,0	; Spare Jump for later use
	DEFB	0C9H,0,0	; Spare Jump for later use

;=================== Main code starts here =======================
CODEBGN EQU	$
;.........................................................................
; User-defined entry routine

USERIN:	LD	HL,(0109H)	; Z3 pointer
	LD	DE,80H		; .80H bytes later..
	ADD	HL,DE
	LD	(VIDPTR),HL	; ..set Z3TCAP pointer
	LD	DE,14H		; Offset to CLS Delay valie
	ADD	HL,DE
	LD	A,(HL)		; .fetch
	LD	(CLSDLY+1),A	; ..store inline
	INC	HL		; Advance to CM Delay value
	LD	A,(HL)		; .fetch
	LD	(CMDLY+1),A	; ..store inline
	INC	HL		; Advance
	INC	HL		; .to CLS String start
	LD	(CLSPTR+1),HL	; ..store inline
	CALL	VIDSKP		; Skip to Next (CM) String Start
	LD	(CMPTR+1),HL	; ..store inline
	CALL	VIDSKP		; Skip over CE String Start
	CALL	VIDSKP		; .advance to SO String Start
	LD	(INVONV+1),HL	; ..and Save inline
	CALL	VIDSKP		; Advance to SE String Start
	LD	(INVOFV+1),HL	; ..and Save inline
	RET

;.........................................................................
; User-defined exit routine.
; If this is NOT a B/P Bios, this routine simply returns with the ASCI0
; parameters in whatever state exists.  If this IS a B/P Bios, the Device
; Initialization routine is called to restore default settings.

USEROUT: LD	HL,(0001H)	; Get BIOS Base address
	LD	L,3*30		; ..offset to Return BIOS Information entry
	LD	A,(HL)		; Get the char
	CP	0C3H		; Is it a Jump?
	RET	NZ		; ..Not B/P Bios if not
	CALL	JPHL		; Call it if it appears Ok
	LD	HL,-6		; "B/P" must be at -6 from Config
	ADD	HL,DE		; ..offset to start of ID string
	LD	A,(HL)		; Get first
	CP	'B'		; Ok?
	RET	NZ		; ..just quit if not
	INC	HL
	LD	A,(HL)		; Get second
	CP	'/'		; Ok?
	RET	NZ		; ..just quit if not
	INC	HL
	LD	A,(HL)		; Finally third
	CP	'P'		; Ok?
	RET	NZ		; ..just quit if Not

	CALL	PRINT		; Else we are under B/P Bios, say so
	DEFB	CR,LF,'...Restoring B/P Bios Defaults...',CR,LF,0
	LD	HL,(0001)	; Get Bios Base address
	LD	L,3*21		; .offset to Device Init Function Jump
JPHL:	JP	(HL)		; ..execute returning thru stack

;.........................................................................

SCRNPR:				; Screen Print Function
SETPORT:			; Set Communications Port Function
SPARE:	RET

;.........................................................................
; Get a character from the modem: return in HL
;  It is not necessary to test for status

AUXIN:	CALL	AUXIST		; Check input status
	JR	Z,AUXIN		; ..loop if Not Ready
	IN0	A,(IDAT0)	; Else read the Char
	LD	L,A		; .place it for return
	LD	H,0		; ..in 16-bit form
	RET

;.........................................................................
; Send a character to the modem

AUXOUT:	LD	HL,2		; Get the character
	ADD	HL,SP
	LD	C,(HL)
AUXOV:	CALL	AUXOST		; Check the Status
	JR	Z,AUXOV		; ..looping if Not ready
	OUT0	(ODAT0),C	; Else send the character
	RET			; ..and return

;.........................................................................
; Test for output ready: return TRUE (1) in HL if ok

AUXOST:	IN0	A,(STAT0)	; Read the Status port
	AND	02H		; Mack for Send Bit
	JR	RDYV		; ..continue below

;.........................................................................
; Test for character at modem: return TRUE (1) in HL if so

AUXIST:	IN0	A,(STAT0)	; Read the Status port
	AND	80H		; Mask for Receive Bit
RDYV:	LD	HL,0		; Assume No char
	RET	Z		; ..return if this is the case
	INC	L		; Else set flag to 1
	LD	A,L		; ..duplicate in A
	RET

;.........................................................................
; Send a break to the modem: leave empty if your system can't do it

SNDBRK:	RET			; Z-180 Can't support Break

;.........................................................................
; Test UART flags for error: return TRUE (1) in HL if error (this is dummy)

MDMERR:	LD	HL,0		; errors processed in BIOS
	XOR	A
	RET			; modem error return

;.........................................................................
; Turn DTR (and optionally RTS) ON.

DTRON:	RET			; DTR not available on modem port,
				; RTS handled internal to BIOS
;.........................................................................
; Turn DTR (and RTS?) OFF

DTROFF:	RET			; DTR not available on modem port,
				; RTS handled internal to BIOS
;.........................................................................
; Initialize the UART

INIT:	LD	HL,2		; get parameters
	ADD	HL,SP
	LD	A,(HL)
	LD	(BRATE),A
	INC	HL
	INC	HL		; bump for next
	LD	A,(HL)		; get lo
	AND	5FH		; Convert to upper case
	LD	(PARITY),A	; parity
	INC	HL
	INC	HL		; bump for next
	LD	A,(HL)		; get lo
	AND	0FH		; Make sure binary
	LD	(DATA),A	; Save data bits
	INC	HL
	INC	HL		; bump for next
	LD	A,(HL)		; get lo
	AND	0FH		; Make sure binary
	LD	(STOP),A	; stop bits
INITX:	DI			; no interrupts while we're playing with
	IN0	B,(CNTLA0)	; the ASCI, please
	LD	A,(STOP)

; -- set up # of stop bits

	CP	2		; one or two stop bits?
	JR	Z,INIT1		; 2 bits asked for 
	RES	0,B		; 1 bit - reset bit 0
	JR	INIT2

INIT1:  SET	0,B		; 2 bits - set bit 0

; -- set up parity enable/disable

INIT2:  RES	1,B		; stop bits set up, set parity (assume none)
	LD	A,(PARITY)
	SUB	'N'		; no parity (bits 0 & 1 reset)?
	JR	Z,INIT3
	SET	1,B
INIT3:	SET	2,B		; assume 8 data bits
	LD	A,(DATA)
	CP	8
	JR	Z,INIT4
	RES	2,B		; 7 data bits
INIT4:	OUT0	(CNTLA0),B

; -- set up odd/even parity, if parity enabled

	BIT	1,B
	JR	Z,INIT6		; jump if no parity
	IN0	B,(CNTLB0)
	SET	4,B		; assume ODD parity
	LD	A,(PARITY)
	CP	'O'
	JR	Z,INIT5
	RES	4,B
INIT5:	OUT0	(CNTLB0),B	; set parity

; -- set up baud rate

INIT6:	LD	HL,(BRATE)	; Get Configured rate (only low byte valid)
	LD	H,0		; .convert to 16-bits
	LD	B,L		; ..save Rate Byte for later
	LD	DE,BTABLE	; Point to Baud Rate Table
	ADD	HL,DE		; index into baud rate table
	LD	A,(HL)		; fetch baud rate code
	OR	A
	JR	NZ,INIT7	; unsupported baud rate?
	LD	A,(MSPEED)	; Get default Speed
	LD	(BRATE),A	; ..and save
	JR	INITGO

INIT7:	IN0	A,(CNTLB0)
	AND	00010000B	; save parity setting
	OR	(HL)		; or in baud rate divisor
	RES	7,A		; make sure valid marker is off
	OUT0	(CNTLB0),A
	LD	A,B
	LD	(MSPEED),A	; set new baud rate in low memory
INITGO:	LD	HL,0
	EI
	RET

; Baud rate factors, output to bauda to select baud rate

BTABLE:
	  IF  [CLKSPD = 6]	; Baud Rate Bits at 6.144 MHz
	DEFB	0		; 0 - 110b (not supported)
	DEFB	00001101B	; 1 - 300b
	DEFB	0		; 2 - 450b (not supported)
	DEFB	00001100B	; 3 - 600b
	DEFB	0		; 4 - 710b (not supported)
	DEFB	00001011B	; 5 - 1200b
	DEFB	00001010B	; 6 - 2400b
	DEFB	00001001B	; 7 - 4800b
	DEFB	00001000B	; 8 - 9600b
	DEFB	00000001B	; 9 - 19.2Kb
	DEFB	00000000B	; 10 - 38.4Kb
	DEFB	0		; 11 - 57.6Kb (not supported)
	DEFB	0		; 12 - 76.8Kb (not supported)
	  ENDIF
	  IF  [CLKSPD = 12]	; Baud Rate Bits at 12.288 MHz
	DEFB	0		; 0 - 110b (not supported)
	DEFB	00001110B	; 1 - 300b
	DEFB	0		; 2 - 450b (not supported)
	DEFB	00001101B	; 3 - 600b
	DEFB	0		; 4 - 710b (not supported)
	DEFB	00001100B	; 5 - 1200b
	DEFB	00001011B	; 6 - 2400b
	DEFB	00001010B	; 7 - 4800b
	DEFB	00001001B	; 8 - 9600b
	DEFB	00001000B	; 9 - 19.2Kb
	DEFB	00000001B	; 10 - 38.4Kb
	DEFB	0		; 11 - 57.6Kb (not supported)
	DEFB	0000000B	; 12 - 76.8Kb
	  ELSE			; (Default) Baud Rate Bits at 9.216 MHz
	DEFB	0		; 0 - 110b (not supported)
	DEFB	00101100B	; 1 - 300b
	DEFB	0		; 2 - 450b
	DEFB	00101011B	; 3 - 600b
	DEFB	0		; 4 - 710b (not supported)
	DEFB	00101010B	; 5 - 1200b
	DEFB	00101001B	; 6 - 2400b
	DEFB	00101000B	; 7 - 4800b
	DEFB	00100001B	; 8 - 9600b
	DEFB	00100000B	; 9 - 19.2Kb
	DEFB	0		; 10 - 38.4Kb (not supported)
	DEFB	80H		; 11 - 57.6KB
	DEFB	0		; 12 - 76.8Kb (not supported)
	  ENDIF

PARITY: DEFB	'N',0		; parity (will be 'N', 'E' or 'O')
DATA:	DEFW	8		; data bits (will be 7 or 8)
STOP:	DEFW	1		; stop bits (will be 1 or 2)
BRATE:  DEFB	9		; temp baud rate location

LINEBUF: DEFS	80

;****************************************************************************
;   Video terminal sequences: Adapted for Z3TCAP access from Syslib 3.6
;----------------------------------------------------------------------------
; Cursor addressing:

CURSADD: LD	HL,2		; get parameters
	ADD	HL,SP
	LD	D,(HL)		; Get Row to H (Base 0)
	INC	HL		; ..advance to Hi byte (ignored)
	INC	HL		; ...and to Lo byte of Column
	LD	E,(HL)		; Get Column (Base 0)
	CALL	CKTCAP		; Is a Termcap installed?
	RET	C		; ..return if Not
CMPTR:	LD	HL,$-$		; Load Ptr to CM String (Set in Init)
	LD	A,(HL)		;get first char of CM string
	OR	A		;if no string, error
	RET	Z
	EX	DE,HL		;DE=address of CM string
	CALL	GXY		;output xy string with delay
CMDLY:	LD	HL,$-$		; Load Cursor Motion Delay (Set in Init)
	JP	WAITHLMS

;.....
; GOTOXY
; Enter: H = Row
;	 L = Column to Position To (0,0 is Home)
;	DE = Address of CM string

GXY:

; Cycle thru string

GXYLOOP: LD	A,(DE)		; Get next Char
	INC	DE		; .pt to next
	OR	A		; Done?
	RET	Z		; ..exit here if so
	CP	'%'		; Command?
	JR	Z,GXYCMD	; ..jump to process if so
	CP	'\'		; Escape?
	JR	NZ,GXYNOR	; ..jump if Normal Character
	LD	A,(DE)		; Else get next literal char
GXYNOX:	INC	DE		; .advance to next
GXYNOR:	CALL	COUT		; Send Character
	JR	GXYLOOP		; ..and loop

; Interpret next character as a Command Character

GXYCMD:	LD	A,(DE)		; Get Command Char
	INC	DE		; .advance to next
	CP	'a'		; Is it less than small-A?
	JR	C,GXYCM0	; ..jump if so
	CP	'z'+1		; Greater than small-Z?
	JR	NC,GXYCM0	; ..jump if so
	AND	5FH		; Else Capatilize
GXYCM0:	CP	'D'		; %D
	JR	Z,GXYOUT1
	CP	'2'		; %2
	JR	Z,GXYOUT2
	CP	'3'		; %3
	JR	Z,GXYOUT3
	CP	'.'		; %.
	JR	Z,GXYOUT4
	CP	'+'		; %+v
	JR	Z,GXYOUT5
	CP	'>'		; %>xy
	JR	Z,GXYGT
	CP	'R'		; %R
	JR	Z,GXYREV
	CP	'I'		; %I
	JR	NZ,GXYNOR	; ..jump to print literal char if Not
			;..else fall thru to..

; I - Set Row/Col Home to 1,1 rather than 0,0

GXYINC:	INC	H		; Set Row to Row + 1
	INC	L		; Set Col to Col + 1
	JR	GXYLOOP		; ..and loop

; R - Reverse order of output to Column then Row (default is Row then Column)

GXYREV:	LD	A,L		; Reverse Row and Col
	LD	L,H
	LD	H,A
	JR	GXYLOOP

; >xy - If value of Row/Col is greater than x, Add y to it

GXYGT:	LD	A,(DE)		; Get value to test
	INC	DE		; .pt to next
	CP	H		; Is value > x?
	JR	NC,GXYGT1	; ..jump if Not
	LD	A,(DE)		; Else get value to add
	ADD	A,C		; .add
	LD	H,A		; ..and put value back
GXYGT1:	INC	DE		; Advance to next
	JR	GXYLOOP		; ..and loop

; +n - Add n to Next Value and Output

GXYOUT5: LD	A,(DE)		;get value to add
	INC	DE		;pt to next
			;..fall thru to..
; . - Output Next Value

GXYOUT4: ADD	A,H		; Add offset
RCMKEV:	CALL	COUT		; .output value
	LD	H,L		; Move any next byte in position
	LD	L,0		; .set any following to Null
	JR	GXYLOOP		; ..back for More

; 3 - Output Next Value as 3 Decimal Digits

GXYOUT3: LD	C,1		; Set to output Leading Zeroes
GXY03A:	LD	A,H		; Get byte to output
	LD	B,100		; .set divisor
	CALL	DIGOUT		; ..and Output first digit
GXYOT3:	LD	B,10		; Output 10's
	CALL	DIGOUT
	ADD	A,'0'		; Output 1's
	JR	RCMKEV		; ..Echo then vector back

; 2 - Output Next Value as 2 Decimal Digits

GXYOUT2: LD	A,H		; Get Value
	LD	C,1		; .set for Leading Zeros
	JR	GXYOT3		; ..and jump to Output

; D - Output Next Value as n Decimal Digits with No Leading Zeroes

GXYOUT1: LD	C,0		; Set for No Leading Zeroes
	JR	GXY03A		; ..and use code above

; Output A as Decimal Digit Character
;   B = Quantity to Subtract from A, C(LSB) = 0 if No Leading Zeros allowed

DIGOUT:	PUSH	DE		;save DE
	LD	D,'0'		;char
DECOT1:	SUB	B		;subtract
	JR	C,DECOT2
	INC	D		;increment char
	JR	DECOT1

DECOT2:	ADD	A,B		;add back in
	PUSH	AF		;save result
	LD	A,D		;get digit
	CP	'0'		;zero?
	JR	NZ,DECOT3
	BIT	0,C		; Does the Zero Flag say to Print Zeros?
DECOT3:	CALL	NZ,COUT		; ..print it if Flag says so
	POP	AF		;get A
	POP	DE		;restore DE
	RET

; GXY Buffers

;;RCORDER: DEFB	0		; 0 = Row/Col, else Col/Row
;;RCBASE:	 DEFB	0		; 0 = Org is 0,0, else Org is 1,1
;;CMDELAY: DEFW	0		; Number of milliseconds to delay for CM

;;ROW:	DEFS	2		; row
COL:	DEFS	2		; Column, Row bytes

;.....
; Skip to end of string.  Exit pointing at start of following string

VIDSKP:	LD	A,(HL)		;get next char
	INC	HL		;pt to next
	OR	A		;done if zero
	RET	Z
	CP	'\'		;literal value?
	JR	NZ,VIDSKP	;continue if not
	INC	HL		;pt to after literal value
	JR	VIDSKP

;.....
; Termcap Pointer

VIDPTR:	DEFW	0		;first byte of termcap entry

;.........................................................................
; Clear screen:

CLS:	CALL	CKTCAP		; Is a TermCap Installed?
	RET	C		; ..return if Not
CLSDLY:	LD	D,$-$		; Load CLS Delay value (Set in Init)
CLSPTR:	LD	HL,$-$		; .load Ptr to CLS String (Set in Init)
	JR	VIDCHV		; ..jump to print string if exists

;.........................................................................
; Inverse video on:

INVON:	CALL	CKTCAP		; Is a TermCap Installed?
	RET	C		; ..return if Not
INVONV:	LD	HL,$-$		; Load Ptr to SO String (Set in Init)
	JR	VIDCHV		; ..jump to print Stand Out (SO) String

;.........................................................................
; Inverse video off:

INVOFF:	CALL	CKTCAP		; Is a TermCap Installed?
	RET	C		; ..return if Not
INVOFV:	LD	HL,$-$		; Load Ptr to SE String (Set in Init)
VIDCHV:	LD	A,(HL)		; Get first char of String
	OR	A		; Any string there?
	RET	Z		; ..quit here if Not
			;..else fall thru to..
;.....
; VIDOUT - Output video string pted to by HL
;	Output also a delay contained in the D register

VIDOUT:	LD	A,(HL)		;get next char
	OR	A		;done if zero
	JR	Z,VID2
	INC	HL		;pt to next
	CP	'\'		;literal value?
	JR	NZ,VID1
	LD	A,(HL)		;get literal char
	INC	HL		;pt to after it
VID1:	CALL	COUT		;output char
	JR	VIDOUT

VID2:	PUSH	HL
	LD	L,D		;output delay
	LD	H,0
	CALL	WAITHLMS	;output delay
	POP	HL
	RET

;.........................................................................
; Check for valid TERMCAP.
; Return: HL = Points to start of TERMCAP if valid, undefined if Not
;	   Carry Set (C) if No Termcap present

CKTCAP:	LD	HL,(VIDPTR)	; Point to Environment Descriptor
	LD	A,(HL)		; Get first char of ID Name
	CP	' '+1		; Anything There?
	RET			; ..return Carry Set if Space (No Tcap)

;****************************************************************************

HIDE:				; Turn Off Cursor
SHOW:				; Turn On Cursor:
SAVECU:				; Save Cursor Position:
RESCU:				; Restore Cursor Position:

MINT:				; Service Modem Interrupt:
INVEC:				; Initialise Interrupt Vectors:
DINVEC:	RET			; De-initialise Interrupt Vectors:

;****************** End of user-defined code ********************************
; Don't change anything below this point. We needed some assembly language
; stuff for speed, and this seemed like a good place to put it.

;.........................................................................
; Modem character test for 100 ms

MRD:	PUSH	BC		; Save BC
	LD	BC,100		; Set Limit
MRD1:	CALL	AUXIST		; Char at Modem?
	JR	NZ,MRD2		; ..jump to Exit if Yes
	LD	HL,1		; Else wait 1ms
	CALL	WAITHLMS
	DEC	BC		; Loop till done
	LD	A,B
	OR	C
	JR	NZ,MRD1
	LD	HL,0		; Nothing there, Result = 0
	XOR	A
MRD2:	POP	BC
	RET

;.........................................................................
; Inline print routine: destroys A and HL

PRINT:	EX	(SP),HL		; get address of string
PLOOP:	LD	A,(HL)		; get next
	INC	HL		; bump pointer
	OR	A		; done if zero
	JR	Z,PDONE
	CALL	COUT		; else print
	JR	PLOOP		; and loop

PDONE:	EX	(SP),HL		; restore return address
	RET			; and quit

;.........................................................................
; Output a character in A to the console

COUT:	PUSH	BC		; save regs
	PUSH	DE
	PUSH	HL
	LD	E,A		; Save the character to E for BDOS routine
	LD	C,2		; BDOS conout routine
	CALL	BDOS		; print it
	POP	HL
	POP	DE
	POP	BC
	RET

;.........................................................................
; Wait(seconds)

WAIT:	LD	HL,2
	ADD	HL,SP
	LD	E,(HL)		; Get Low byte of Parm
	INC	HL
	LD	D,(HL)		; .get High byte
	INC	HL		; ..bump to pt to next
	EX	DE,HL		; ...put Parm in HL
			; fall thru to..
; Wait seconds in HL

WAITHLS: PUSH	BC		; Save BC
	 PUSH	DE		; .DE

; Calculate values for loop constants. Need to have two loops to avoid
;   16-bit overflow with clock speeds above 9 MHz.

OUTERVAL	EQU	(CLKSPD / 10) + 1
INNERVAL	EQU	(6667 / OUTERVAL) * CLKSPD

WAIT10:	LD	B,OUTERVAL
WAIT11:	LD	DE,INNERVAL
WAIT12:	BIT	0,(IX)		; time-wasters
	BIT	0,(IX)
	BIT	0,(IX)		; 20 T-states each
	BIT	0,(IX)
	BIT	0,(IX)
	BIT	0,(IX)
	DEC	DE
	LD	A,E
	LD	A,D
	OR	E
	JR	NZ,WAIT12	; 150 T-states per Inner Loop
	DJNZ	WAIT11		; Decrement Outer Loop
	DEC	HL		; Ok, decrement count in HL
	LD	A,H
	OR	L
	JR	NZ,WAIT10
	POP	DE		; Done -- restore DE
	POP	BC		; .and BC
	RET

;.........................................................................
; Wait milliseconds

MSWAIT:	LD	HL,2
	ADD	HL,SP
	LD	E,(HL)		; Get Low byte of Parm
	INC	HL
	LD	D,(HL)		; .get High byte
	INC	HL		; ..bump to pt to next
	EX	DE,HL		; ...put Parm in HL
			; fall thru to..
; Wait milliseconds in HL

WAITHLMS:
	LD	A,H
	OR	L
	RET	Z
	PUSH	DE
W1MS0:	LD	DE,39 * CLKSPD
W1MS1:	DEC	DE
	LD	A,D
	OR	E
	JR	NZ,W1MS1
	DEC	HL
	LD	A,H
	OR	L
	JR	NZ,W1MS0
	POP	DE
	RET

;.........................................................................
; Get address of user-defined variables

GETVARS: LD	HL,USRVARS
	 RET

USRVARS: DEFW	OVRDRV		; .OVR etc. Drive/User
	 DEFW	OVRUSR

	END