;::::::::::::::::::::::::::::::::::::::::::::******************************
;	  Floppy Disk Routines		     ***** Hardware Dependent *****
;   - Retro-Brew Hardware with HBIOS -	     ******************************
;
; 1.4 - 27 Mar 14 - Initial N8VEM test release 			      WW+LN
; 1.3 - 26 Aug 01 - Cleaned up for GPL Release.				HFB
; 1.2c- 12 May 97 - Cleaned up source, modified STSIZE Code (again).	HFB
; 1.2b- 22 Apr 97 - Changed 5.25" Hi/Lo Speed controls.			HFB
; 1.0a- 23 Mar 97 - (test) fixes.					HFB
; 1.0 - 13 Aug 96 - Initial Release for P112 from YASMIO.		HFB
;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; Floppy Units are accessed on Retro-Brew systems using HBIOS function
; calls.  These functions include read, write, status and media type.
; For 3.5" drive there are two media types.  For 5.25" drive two media
; types are supported, while for 8" drives one type is supported. 
; Only high density is supported on 3.5" drives either single or double
; sided.  For 5.25" drive either double or high density is supported on
; double sided disks.  Only double density double sided 8" disks are 
; supported.  Many BPBIOS floppy routines are stubbed such as DMA support
; and motor control since all these details are handled behind the scene by
; HBIOS.  Currently HBIOS handles the head given the track and sector so 
; the interface treats all floppies as single sided.

	  IF  BANKED
	COMMON	/BANK2/
	  ELSE
	CSEG
	  ENDIF

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; STMODE  (Function 0) - Set the FDC mode for Read/Write operations.
;
; Enter	:  A = Single-Density Flag (0 = Double Dens, 0FFH = Single Dens)
; Return: Nothing
; Uses	: AF		All other Registers Preserved/Not Affected
;
; Assumes STSIZE and STSECT called first
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

STMODE:	CALL	PANIC

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; STSIZE  (Function 1) - Set Drive Size (3.5", 5.25", 8"), Drive Speed
;  (High/Low) Capability, and a Boolean flag for whether Motor Control is
;  needed by the Drive.
;
; Enter :  A = Hi Speed Flag ( 0 = Normal, 0FFH = High Speed Capable)
;	   D = Motor Flag (0 = No Motor Control, 0FFH = Motor needed)
;	   E = Drive Size (0 = Hard, 001 = 8", 010 = 5.25", 011 = 3.5")
; Return: Nothing
; Uses	: AF		All other Registers Preserved/Not Affected
;
; Assumes STHDRV Called Previously.   Call before calling STMODE.
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

STSIZE:	CALL	PANIC

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; STHDRV  (Function 2) - Set Head and Drive for Disk Operations.
;
; Enter :  A = Unit # in D0-D1, Head in D2
; Return: Nothing
; Uses	: AF		All other Registers Preserved/Not Affected
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

STHDRV:	CALL	PANIC

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; STSECT  (Function 3) - Set Sector Number, Sector Size and Last Sector #
;
; Enter :  A = Physical Sector Number
;	   D = Sector Size (0=128, 1=256, 2=512, 3=1024)
;	   E = Last Physical Sector # on Side
; Return: Nothing
; Uses  : AF		All other Registers Preserved/Not Affected
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

STSECT:	CALL	PANIC

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; SPEC  (Function 4) - Do a Specify Command, setting Step Rate and Head
;  Load/Unload Time.  Values are rounded up if not even increments.
;
; Enter :  A = Step Rate (in mS;  Bit 7 = 1 for 8" drive
;	   D = Head Unload Time (in mS)
;	   E = Head Load Time (in mS)
; Return: Nothing
; Uses	: AF		All other Registers Preserved/Not Affected
;
; Assumes STSIZE called previously to set DRVSPD variable.
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

SPEC:	CALL	PANIC

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; RECAL  (Function 5) - Recalibrate Drive (moves heads to track 0).
;
; Enter	: Nothing
; Return:  A = 0 if Ok, NZ if Error.  Flags reflect A
; Uses	: AF		All other Registers Preserved/Not Affected
;
; NOTE: BC Must be preserved by this routine.
; Assumes STHDRV, SPEC, STSIZE and STMODE called first.
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

RECAL:	CALL	PANIC

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; SEEK   (Function 6) - Set the Track for disk operations and seek to it.
;
; Enter :  A = Desired Track Number
;	   D = Verify flag (0=No, FF=Yes)
;	   E = Double-step Flag (E <> 0 for Double-step)
; Return:  A = 0, Zero Flag Set (Z) if Ok, A <> 0 Zero Clear (NZ) if Error
; Uses  : AF		All other Registers Preserved/Not Affected
;
; Assumes STHDRV, SPEC, STSIZE and STMODE are called first.
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

SEEK:	CALL	PANIC
	XOR	A
	RET

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; SREAD  (Function 7) - Read a Sector from the Floppy Disk.  The Mode,
;  Head/Drive, Track, and Sector must have already been set.
;
; Enter : HL --> Read Buffer
; Return:  A = 0, Zero Set (Z) if Ok, A <> 0, Zero Clear (NZ) if Error.
; Uses	: AF,HL.	All other Registers Preserved/Not Affected
;
; Assumes STMODE, STHDRV, STSECT, SPEC and SEEK Called First.
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

SREAD:	CALL	PANIC
	XOR	A
	RET

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; SWRITE  (Function 8) - Write a Sector to the Floppy Disk.  The Mode,
;  Head/Drive, Track, and Sector must have already been set.
;
; Enter : HL --> Write Buffer
; Return:  A = 0, Zero Flag Set (Z) if Ok, A <> 0 Zero Clear (NZ) if Errors
; Uses	: AF,HL.	All other registers Preserved/Not Affected.
; Assumes STMODE, STHDRV, STSECT, SPEC and SEEK Called First.
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

SWRITE:	CALL	PANIC
	XOR	A
	RET

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; READID  (Function 9) - Read the first Valid Address Mark on a track.
;
; Enter : Nothing
; Return:  A = 0 if Ok, NZ if Error.  Flags reflect A
; Uses	: AF		All other Registers Preserved/Not Affected
;
; Assumes STHDRV, SPEC, STSIZE and STMODE called first.
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

READID:	CALL	PANIC
	XOR	A
	RET

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; RETDST (Function 10) - Return the status of a drive.
;  This routine reports a "765" Controller type instead of actual number.
;
; Enter : Nothing
; Return:  A = Status byte
;	  BC = 765 (FDC Controller Type)
;	  HL = Address of Status Byte
; Uses  : AF,BC,HL		All other Registers Preserved/Not Affected
;
; Assumes STHDRV called first
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

RETDST:	CALL	PANIC
	;LD	HL,ST0		; Point to Status Byte (Reg 3 contents)
	;LD	A,(HL)		;  fetch it
	;LD	BC,765		;   load Controller ID
	RET

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; FMTTRK  (Function 11) - Format a complete track on one side of a Floppy
;  Disk.  The Mode, Head/Drive, Track, and Sector must have been set.
;
; NOTE: The contents of the Format Data Block varies between controllers,
;  so RETDST should be called to determine the controller type before
;  setting up data structures.
;
; Enter :  D = Formatting Sctrs/Track value
;	   E = Formatting Gap 3 Byte Count
;	  HL = Pointer to Controller-dependent Format Data block
; Return:  A = 0, Zero Flag Set (Z) if Ok, A <> 0 Zero Clear (NZ) if Errors
; Uses  : All Primary Registers
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

FMTTRK:	CALL	PANIC
	;XOR	A
	RET

;=============================================================================
; FDCMD - Send Command to FDC
; Enter:  B = # of Bytes in Command, C = Command Byte
;	 HL -> Buffer for Read/Write Data (If Needed)
; Exit : AF = Status byte
; Uses : AF,BC

FDCMD:	CALL	PANIC
	;LD	A,(ST0)		; Else get first byte of Status
	;AND	0C0H		;  check for Normal termination
	RET			; ..return w/Error Flags set

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; MOTOR CONTROL.  This routine performs final selection of the drive control
;  latch and determines if the Motors are already spinning.  If they are off
;  and Motor control is needed, then the Motors are activated and the spinup
;  delay time in tenths-of-seconds is performed before returning.
;
; Enter : Command byte in A
; Return: Head Delay bit set in Command in A if needed
; Uses  : None.  All Registers Preserved/Not Affected

MOTOR:	CALL	PANIC
	XOR	A
	RET

;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
; Hardware-Dependent Host Read/Write Routine linked to from FLOPPY module.
;  This routine Reads/Writes data from HSTBUF trying up to MXRTRY times
;  before giving up.  If an error occurs after the next-to-last try, the
;  heads are homed to force a re-seek.
;
; Enter:  (RDOP Set for desired operation)
; Exit :  A = 0, Zero Set if Ok, A <> 0, Zero Reset if Errors
; Uses : AF,HL
;
; RDOP is set to 1 for Read, 0 for Write, TTRK set with desired Track
;  number, STHDRV, STSECT, STMODE, SPEC all called previously.
;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

FHDRW:	CALL	PANIC
	;XOR	A
	RET


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

	CSEG		;*** Remainder of Code MUST be in Main Memory ***
	
;========================================================================
; Reset the Floppy Disk Controller.  Called from CBOOT in case of Hard
; Disk Boot which leaves the controller in a "hung" state, and locally
; if the Controller times out (often due to changing diskettes).

FDRst:	CALL	PANIC
	RET

;========================================================================
; Motor Off routine.  Called from SELFLP2 which forces
; Motors/Timer to be Off state so spinup delay is forced on next selection.

MOTOFF:	CALL	PANIC
ChgSpd:	RET

;======================== RAM Storage Area ==============================

	  IF  BANKED
	COMMON	/B2RAM/		; If banked, Local stack in Bank
	  ELSE
	DSEG			; ..otherwise in Data Segment
	  ENDIF			;

	DSEG			; Place in Common memory

; NOTE: Variables listed as (** Global **) are accessed by other modules and
;	MUST exist as defined.

HDR:	DEFS	1		; Head (B2), Drive (B0,1)	(** Global **)

; FDC Operation Result Storage Area

;ST0:	DEFS	1		; Status Byte 0
;ST1:	DEFS	1		; Status Byte 1 (can also be PCN)
;ST2:	DEFS	1		; Status Byte 2
RC:	DEFS	1		; Track #			(** Global **)
;RH:	DEFS	1		; Head # (0/1)
RR:	DEFS	1		; Sector #			(** Global **)
RN:	DEFS	1		; Sector Size			(** Global **)

;-->>>  Do NOT re-order the following two bytes !! <<<--

;MTM:	DEFS	1		; Floppy Time down-counter
;MOTIM:	DEFS	1		; Motor On Time Counter

; DISK Subsystem Variable Storage

;FDMOT:	DEFS	1		; Motor on required flag
RDOP:	DEFS	1		; Read/write flag
;RETRYS:	DEFS	1		; Number of times to try Opns
;RWRTRY:	DEFS	1		; Number of read/write tries
;DRVSPD:	DEFS	1		; Drive Speed
;DRVSIZ:	DEFS	1		; Drive Size
STEP2:	DEFS	1		; <> 0 for Double Step		(** Global **)
;MODE:	DEFS	1		; Bit 6 = 1 if MFM, 0 = FM
;ACTIVE:	DEFS	1		; Current bits written to Dev Contr Reg (DCR)
;DLYCNT:	DEFS	1		; Delay value reading Main Status Reg
;FSPT:	DEFS	1		; Format Sectors/Track value
TSBSCF:	DEFS	1		; 0=Hd always 0 (TSBSC)		(** Global **)

TTRK:	DEFS	1		; Storage for Track		(** Global **)
;TRKARY:	DEFS	4		; Track storage locations for four drives

;=========================== End of FDC-WW ==============================