From 364e48a5d3f77a442498fd4063903868744d7c01 Mon Sep 17 00:00:00 2001
From: Wayne Warthen <wwarthen@gmail.com>
Date: Fri, 26 May 2023 16:48:13 -0700
Subject: [PATCH] IMM Driver Cleanup, PPA Driver Skeleton

IMM Driver has rational timeouts now.  It also lights the MG014 LED during activity.
The PPA skeleton just attempts to determine if the PPA interface is present.  It does not attempt any I/O.
---
 Source/CBIOS/cbios.asm |    7 +
 Source/CPM3/boot.z80   |    9 +-
 Source/HBIOS/hbios.asm |    2 -
 Source/HBIOS/imm.asm   |  619 ++++++++++++---------
 Source/HBIOS/lpt.asm   |    2 +-
 Source/HBIOS/ppa.asm   | 1182 +++++++++++-----------------------------
 Source/HBIOS/ppp.asm   |    2 +-
 Source/HBIOS/std.asm   |   10 +
 Source/ver.inc         |    2 +-
 Source/ver.lib         |    2 +-
 10 files changed, 690 insertions(+), 1147 deletions(-)

diff --git a/Source/CBIOS/cbios.asm b/Source/CBIOS/cbios.asm
index 97771883..0b06d19c 100644
--- a/Source/CBIOS/cbios.asm
+++ b/Source/CBIOS/cbios.asm
@@ -2929,6 +2929,12 @@ DRV_INIT3:
 	RET
 ;
 DRV_INIT3A:
+	; CHECK FOR HARD DISK REMOVABLE CARTRIDGE DRIVES
+	CP	DIODEV_PPA		; PPA (ZIP DRIVE) IS REMOVABLE
+	JR	Z,DRV_INIT3B		; IF SO, SKIP MEDIA CHECK
+	CP	DIODEV_IMM		; IMM (ZIP DRIVE) IS REMOVABLE
+	JR	Z,DRV_INIT3B		; IF SO, SKIP MEDIA CHECK
+
 	; CHECK FOR ACTIVE AND RETURN IF NOT
 	PUSH	DE			; SAVE DE (HARD DISK VOLUME COUNTER)
 	PUSH	HL			; SAVE DRIVE LIST PTR
@@ -2944,6 +2950,7 @@ DRV_INIT3A:
 
 	RET	NZ			; IF NO MEDIA, JUST RETURN
 
+DRV_INIT3B:
 	; IF ACTIVE...
 	LD	(HL),C			; SAVE UNIT NUM IN LIST
 	INC	HL			; BUMP PTR
diff --git a/Source/CPM3/boot.z80 b/Source/CPM3/boot.z80
index ce3fef1b..05dcb4f6 100644
--- a/Source/CPM3/boot.z80
+++ b/Source/CPM3/boot.z80
@@ -181,6 +181,12 @@ dinit3:
 	ret
 ;
 dinit3a:
+	; check for hard disk removable cartridge drives
+	cp	0A0h			; ppa (zip drive) is removable
+	jr	z,dinit3b		; if so, skip media check
+	cp	0B0h			; imm (zip drive) is removable
+	jr	z,dinit3b		; if so, skip media check
+
 	; check for active and return if not
 	push	de			; save de (hard disk volume counter)
 	push	hl			; save drive list ptr
@@ -195,7 +201,8 @@ dinit3a:
 	pop	de			; restore de
 	
 	ret	nz			; if no media, just return
-	
+
+dinit3b:
 	; if active...
 	ld	(hl),c			; save unit num in list
 	inc	hl			; bump ptr
diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index be5110c8..4af09d42 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -6786,7 +6786,6 @@ PS_PRTDC:
 	RES	7,D			; CLEAR LBA BIT
 	LD	B,11			; 11 BIT SHIFT TO CONVERT BLOCKS --> MB
 	CALL	SRL32			; RIGHT SHIFT
-	;CALL	PRTDEC			; PRINT LOW WORD IN DECIMAL (HIGH WORD DISCARDED)
 	CALL	PRTDEC32		; PRINT DWORD IN DECIMAL
 	PRTS("MB$")			; PRINT SUFFIX
 	CALL	PC_COMMA
@@ -6801,7 +6800,6 @@ PS_PRTDC1:
 	RES	7,D			; CLEAR LBA BIT
 	LD	B,1			; 11 BIT SHIFT TO CONVERT BLOCKS --> MB
 	CALL	SRL32			; RIGHT SHIFT
-	;CALL	PRTDEC			; PRINT LOW WORD IN DECIMAL (HIGH WORD DISCARDED)
 	CALL	PRTDEC32		; PRINT DWORD IN DECIMAL
 	PRTS("KB$")			; PRINT SUFFIX
 	CALL	PC_COMMA
diff --git a/Source/HBIOS/imm.asm b/Source/HBIOS/imm.asm
index 7c1b63ec..df3e8301 100644
--- a/Source/HBIOS/imm.asm
+++ b/Source/HBIOS/imm.asm
@@ -13,6 +13,7 @@
 ; MUCH OF THE CODE IS DERIVED FROM FUZIX (ALAN COX).
 ;
 ; 5/23/2023 WBW - INITIAL RELEASE
+; 5/26/3023 WBW - CLEAN UP, LED ACTIVITY
 ;
 ;=============================================================================
 ;
@@ -43,25 +44,16 @@
 ;
 ; TODO:
 ;
-; - TIMEOUT IS INFINITE!!!
-;
-; - ASSIGN DRIVE LETTERS EVEN WHEN NO MEDIA AT BOOT
+; - CLEAN UP WAIT LOOP STUFF
 ;
 ; - OPTIMIZE READ/WRITE LOOPS
 ;
-; - COMMENT MORE OF THE CODE
-;
-; - THERE ARE CURRENTLY NO BUFFER OVERRUN CHECKS.  WE ASSUME SCSI
-;   DEVICES WILL SEND/REQUEST THE EXPECTED NUMBER OF BYTES.
-;
-; - MAKE THE MG014 STATUS LED DO SOMETHING USEFUL?
-;
 ; NOTES:
 ;
-; - THIS DRIVER IS FOR THE ZIP DRIVE EMM INTERFACE.  IT WILL SIMPLY
+; - THIS DRIVER IS FOR THE ZIP DRIVE IMM INTERFACE.  IT WILL SIMPLY
 ;   FAIL TO EVEN RECOGNIZE A ZIP DRIVE WITH THE OLDER PPA INTERFACE.
 ;   THERE DOES NOT SEEM TO BE A WAY TO VISUALLY DETERMINE IF A ZIP
-;   DRIVE IS EMM OR PPA.  SIGH.
+;   DRIVE IS IMM OR PPA.  SIGH.
 ;
 ; - THERE ARE SOME HARD CODED TIMEOUT LOOPS IN THE CODE.  THEY ARE
 ;   WORKING OK ON A 7 MHZ Z80.  THEY ARE LIKELY TO NEED TWEAKING ON
@@ -76,6 +68,9 @@
 ;   THE STANDARD IBM PARALLEL PORT WHICH NECESSITATES A BUNCH OF EXTRA
 ;   BIT FIDDLING ON EVERY READ.
 ;
+; - SOME OF THE DATA TRANSFERS HAVE NO BUFFER OVERRUN CHECKS.  IT IS
+;   ASSUMED SCSI DEVICES WILL SEND/REQUEST THE EXPECTED NUMBER OF BYTES.
+;
 ; IMM PORT OFFSETS
 ;
 IMM_IODATA	.EQU	0		; PORT A, DATA, OUT
@@ -87,17 +82,6 @@ IMM_IOSETUP	.EQU	3		; PPI SETUP
 ;
 IMM_SELF	.EQU	7
 IMM_TGT		.EQU	6
-;
-; SCSI COMMAND CODES
-;
-SCSI_CMD_READ	.EQU	$08
-SCSI_CMD_INQ	.EQU	$12
-SCSI_CMD_TEST	.EQU	$00
-SCSI_CMD_START	.EQU	$1B
-SCSI_CMD_SENSE	.EQU	$03
-SCSI_CMD_WRITE	.EQU	$0A
-SCSI_CMD_RDCAP	.EQU	$25
-
 ;
 ; IMM DEVICE STATUS
 ;
@@ -223,12 +207,18 @@ IMM_DETECT:
 	LD	C,A			; MOVE TO C FOR I/O
 	LD	A,$82			; CONFIG A OUT, B IN, C OUT
 	OUT	(C),A			; DO IT
-	CALL	DELAY
+	CALL	DELAY			; BRIEF DELAY FOR GOOD MEASURE
 ;
+	; WE USE THIS SEQUENCE TO DETECT AN ACTUAL IMM DEVICE ON THE
+	; PARALLEL PORT.  THE VALUES RECORDED IN THE FINAL CALL TO
+	; IMM_DISCONNECT ARE USED TO CONFIRM DEVICE PRESENCE.
+	; NO ACTUAL SCSI COMMANDS ARE USED.
 	CALL	IMM_DISCONNECT
 	CALL	IMM_CONNECT
 	CALL	IMM_DISCONNECT
 ;
+	; THE IMM_SN VALUES ARE RECORDED IN THE CPP ROUTINE USED BY
+	; IMM_CONNECT/DISCONNECT.
 	; EXPECTING S1=$B8, S2=$18, S3=$38
 	LD	A,(IMM_S1)
 	CP	$B8
@@ -273,18 +263,18 @@ IMM_DEFMED:
 ;
 ;
 IMM_READ:
-	CALL	HB_DSKREAD
-	LD	A,SCSI_CMD_READ
-	LD	(IMM_CMD_RW),A
-	JP	IMM_IO
+	CALL	HB_DSKREAD		; HOOK DISK READ CONTROLLER
+	LD	A,SCSI_CMD_READ		; SETUP SCSI READ
+	LD	(IMM_CMD_RW),A		; AND SAVE IT IN SCSI CMD
+	JP	IMM_IO			; DO THE I/O
 ;
 ;
 ;
 IMM_WRITE:
-	CALL	HB_DSKREAD
-	LD	A,SCSI_CMD_WRITE
-	LD	(IMM_CMD_RW),A
-	JP	IMM_IO
+	CALL	HB_DSKREAD		; HOOK DISK WRITE CONTROLLER
+	LD	A,SCSI_CMD_WRITE	; SETUP SCSI WRITE
+	LD	(IMM_CMD_RW),A		; AND SAVE IT IN SCSI CMD
+	JP	IMM_IO			; DO THE I/O
 ;
 ;
 ;
@@ -292,7 +282,7 @@ IMM_IO:
 	LD	(IMM_DSKBUF),HL		; SAVE DISK BUFFER ADDRESS
 	CALL	IMM_CHKERR		; CHECK FOR ERR STATUS AND RESET IF SO
 	JR	NZ,IMM_IO3		; BAIL OUT ON ERROR
-;	
+;
 	; SETUP LBA
 	; 3 BYTES, LITTLE ENDIAN -> BIG ENDIAN
 	LD	HL,IMM_CMD_RW+1		; START OF LBA FIELD IN CDB (MSB)
@@ -307,11 +297,11 @@ IMM_IO:
 	INC	HL
 ;
 	; DO SCSI IO
-	LD	DE,(IMM_DSKBUF)
-	LD	BC,512
-	LD	HL,IMM_CMD_RW
-	CALL	IMM_RUNCMD
-	CALL	Z,IMM_CHKCMD
+	LD	DE,(IMM_DSKBUF)		; DISK BUFFER TO DE
+	LD	BC,512			; ONE SECTOR, 512 BYTES
+	LD	HL,IMM_CMD_RW		; POINT TO READ/WRITE CMD TEMPLATE
+	CALL	IMM_RUNCMD		; RUN THE SCSI ENGINE
+	CALL	Z,IMM_CHKCMD		; IF EXIT OK, CHECK SCSI RESULTS
 	JR	NZ,IMM_IO2		; IF ERROR, SKIP INCREMENT
 	; INCREMENT LBA
 	LD	A,IMM_LBA		; LBA OFFSET
@@ -343,7 +333,7 @@ IMM_STATUS:
 ;
 ;
 IMM_RESET:
-	JP	IMM_INITDEV
+	JP	IMM_INITDEV		; JUST (RE)INIT DEVICE
 ;
 ;
 ;
@@ -363,7 +353,7 @@ IMM_MEDIA:
 	OR	A			; SET FLAGS
 	JR	Z,IMM_MEDIA1		; JUST REPORT CURRENT STATUS AND MEDIA
 ;
-	CALL	IMM_RESET		; RESET IMM INTERFACE
+	CALL	IMM_RESET		; RESET INCLUDES MEDIA CHECK
 ;
 IMM_MEDIA1:
 	LD	A,(IY+IMM_STAT)		; GET STATUS
@@ -418,64 +408,81 @@ IMM_GEOM:
 ; FUNCTION SUPPORT ROUTINES
 ;=============================================================================
 ;
+; OUTPUT BYTE IN A TO THE DATA PORT
+;
 IMM_WRITEDATA:
-	LD	C,(IY+IMM_IOBASE)
-	OUT	(C),A
-	CALL	DELAY
-	RET
+	LD	C,(IY+IMM_IOBASE)	; DATA PORT IS AT IOBASE
+	OUT	(C),A			; WRITE THE BYTE
+	;CALL	DELAY			; IS THIS NEEDED???
+	RET				; DONE
 ;
 ;
 ;
 IMM_WRITECTRL:
-	XOR	$0B
-	LD	C,(IY+IMM_IOBASE)
-	INC	C
+	; IBM PC INVERTS ALL BUT C2 ON THE BUS, MG014 DOES NOT.
+	; BELOW TRANSLATES FROM IBM -> MG014.	IT ALSO INVERTS THE
+	; MG014 LED SIMPLY TO MAKE IT EASY TO KEEP LED ON DURING
+	; ALL ACTIVITY.
+	XOR	$0B | $80		; HIGH BIT IS MG014 LED
+	LD	C,(IY+IMM_IOBASE)	; GET BASE IO ADDRESS
+	INC	C			; BUMP TO CONTROL PORT
 	INC	C
-	OUT	(C),A
-	CALL	DELAY
-	RET
+	OUT	(C),A			; WRITE TO CONTROL PORT
+	;CALL	DELAY			; IS THIS NEEDED?
+	RET				; DONE
 ;
+; READ THE PARALLEL PORT INPUT LINES (STATUS) AND MAP SIGNALS FROM
+; MG014 TO IBM STANDARD.  NOTE POLARITY CHANGE REQUIRED FOR BUSY.
 ;
+; 	MG014		IBM PC
+;	--------	--------
+;	0: /ACK		6: /ACK
+;	1: BUSY		7: /BUSY
+;	2: POUT		5: POUT
+;	3: SEL		4: SEL
+;	4: /ERR		3: /ERR
 ;
 IMM_READSTATUS:
-	LD	C,(IY+IMM_IOBASE)
-	INC	C
-	IN	A,(C)
+	LD	C,(IY+IMM_IOBASE)	; IOBASE TO C
+	INC	C			; BUMP TO STATUS PORT
+	IN	A,(C)			; READ IT
 	LD	C,0			; INIT RESULT
-;	
-	BIT	0,A			; ACK = $01
+;
+	; SHUFFLE BITS
+	BIT	0,A			; 0: /ACK
 	JR	Z,IMM_READSTATUS1
-	SET	6,C			; $40
+	SET	6,C			; 6: /ACK
 ;
 IMM_READSTATUS1:
-;	
-	BIT	1,A			; BUSY = $02
-	JR	NZ,IMM_READSTATUS2
-	SET	7,C			; $80
+;
+	BIT	1,A			; 1: BUSY
+	JR	NZ,IMM_READSTATUS2	; POLARITY CHANGE!
+	SET	7,C			; 7: /BUSY
 ;
 IMM_READSTATUS2:
-;	
-	BIT	2,A			; PAPER = $04
+;
+	BIT	2,A			; 2: POUT
 	JR	Z,IMM_READSTATUS3
-	SET	5,C			; $20
+	SET	5,C			; 5: POUT
 ;
 IMM_READSTATUS3:
-;	
-	BIT	3,A			; SELECT = $08
+;
+	BIT	3,A			; 3: SEL
 	JR	Z,IMM_READSTATUS4
-	SET	4,C			; $10
+	SET	4,C			; 4: SEL
 ;
 IMM_READSTATUS4:
-;	
-	BIT	4,A			; FAULT = $10
+;
+	BIT	4,A			; 4: /ERR
 	JR	Z,IMM_READSTATUS5
-	SET	3,C			; $08
+	SET	3,C			; 3: /ERR
 ;
 IMM_READSTATUS5:
-	LD	A,C
+	LD	A,C			; RESULT TO A
 	RET
 ;
-;
+; SIGNAL SEQUENCE TO CONNECT/DISCONNECT
+; VALUE IN A IS WRITTEN TO DATA PORT DURING SEQUENCE
 ;
 IMM_CPP:
 	PUSH	AF
@@ -516,7 +523,7 @@ IMM_CPP:
 	; CONNECT: S1=$B8 S2=$18 S3=$30
 	; DISCONNECT: S1=$B8 S2=$18 S3=$38
 ;
-#IF (IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nCPP: S1=$")
 	LD	A,(IMM_S1)
 	CALL	PRTHEXBYTE
@@ -535,7 +542,7 @@ IMM_S1	.DB	0
 IMM_S2	.DB	0
 IMM_S3	.DB	0
 ;
-;
+; SEQUENCE TO CONNECT TO DEVICE ON PARALLEL PORT BUS.
 ;
 IMM_CONNECT:
 	LD	A,$E0
@@ -546,14 +553,20 @@ IMM_CONNECT:
 	CALL	IMM_CPP
 	RET
 ;
-;
+; SEQUENCE TO DISCONNECT FROM DEVICE ON PARALLEL PORT BUS.
+; THE FINAL IMM_WRITECTRL IS ONLY TO TURN OFF THE MG014 STATUS LED.
 ;
 IMM_DISCONNECT:
 	LD	A,$30
 	CALL	IMM_CPP
-	RET
 ;
+	; TURNS OFF MG014 LED
+	LD	A,$8C
+	CALL	IMM_WRITECTRL
+;
+	RET
 ;
+; INITIATE A SCSI BUS RESET.
 ;
 IMM_RESETPULSE:
 	LD	A,$04
@@ -574,10 +587,10 @@ IMM_RESETPULSE:
 	CALL	IMM_WRITECTRL
 	RET
 ;
-;
+; SCSI SELECT PROCESS
 ;
 IMM_SELECT:
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nSELECT: $")
 #ENDIF
 	LD	A,$0C
@@ -598,13 +611,14 @@ IMM_SELECT1:
 IMM_SELECT2:
 	LD	A,$04
 	CALL	IMM_WRITECTRL
+	; PLACE HOST AND TARGET BIT ON DATA BUS
 	LD	A,$80 | (1 << IMM_TGT)
 	CALL	IMM_WRITEDATA
-	CALL	DELAY
+	CALL	DELAY			; CONFIRM DELAY TIME?
 	LD	A,$0C
 	CALL	IMM_WRITECTRL
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	IMM_READSTATUS
 	CALL	PC_SPACE
 	CALL	PRTHEXBYTE
@@ -613,7 +627,7 @@ IMM_SELECT2:
 	LD	A,$0D
 	CALL	IMM_WRITECTRL
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	IMM_READSTATUS
 	CALL	PC_SPACE
 	CALL	PRTHEXBYTE
@@ -623,12 +637,12 @@ IMM_SELECT2:
 ;
 IMM_SELECT3:
 	CALL	IMM_READSTATUS
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	PC_SPACE
 	CALL	PRTHEXBYTE
 #ENDIF
 	AND	$08
-	JR	NZ,IMM_SELECT4		; IF CLEAR, MOVE ON
+	JR	NZ,IMM_SELECT4		; IF SET, MOVE ON
 	DEC	HL
 	LD	A,H
 	OR	L
@@ -642,99 +656,123 @@ IMM_SELECT4:
 	XOR	A
 	RET
 ;
+; SEND SCSI CMD BYTE STRING.  AT ENTRY, HL POINTS TO START OF
+; COMMAND BYTES.  THE LENGTH OF THE COMMAND STRING MUST PRECEED
+; THE COMMAND BYTES (HL - 1).
 ;
+; NOTE THAT DATA IS SENT AS BYTE PAIRS!  EACH LOOP SENDS 2 BYTES.
+; DATA OUTPOUT IS BURSTED (NO CHECK FOR BUSY).  SEEMS TO WORK FINE.
 ;
 IMM_SENDCMD:
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nSENDCMD:$")
 #ENDIF
 ;
-	LD	HL,0
+	DEC	HL		; BACKUP TO LENGTH BYTE
+	LD	B,(HL)		; PUT IN B FOR LOOP COUNTER
+;
+#IF (IMMTRACE >= 3)
+	LD	A,B
+	CALL	PC_SPACE
+	CALL	PRTHEXBYTE
+	PRTS(" BYTES$")
+#ENDIF
+;
+	INC	HL		; BACK TO FIRST CMD BYTE
 IMM_SENDCMD1:
-	PUSH	HL
-	CALL	IMM_WAITDONE
-	POP	HL
-	CP	$A8
-	JR	NZ,IMM_SENDCMD2
 	LD	A,$04
 	CALL	IMM_WRITECTRL
-	LD	A,(DE)
+	LD	A,(HL)		; LOAD CMD BYTE
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	PC_SPACE
 	CALL	PRTHEXBYTE
 #ENDIF
 ;
-	CALL	IMM_WRITEDATA
-	INC	DE
-	INC	HL
+	CALL	IMM_WRITEDATA	; PUT IT ON THE BUS
+	INC	HL		; BUMP TO NEXT BYTE
+	DEC	B		; DEC LOOP COUNTER
 	LD	A,$05
 	CALL	IMM_WRITECTRL
-	LD	A,(DE)
+	LD	A,(HL)		; LOAD CMD BYTE
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	PC_SPACE
 	CALL	PRTHEXBYTE
 #ENDIF
 ;
-	CALL	IMM_WRITEDATA
-	INC	DE
-	INC	HL
+	CALL	IMM_WRITEDATA	; PUT IT ON THE BUS
+	INC	HL		; BUMP TO NEXT BYTE
 	LD	A,$00
 	CALL	IMM_WRITECTRL
-	JR	IMM_SENDCMD1
+	DJNZ	IMM_SENDCMD1	; LOOP TILL DONE
 ;
 IMM_SENDCMD2:
 	LD	A,$04
 	CALL	IMM_WRITECTRL
-;
-#IF IMMTRACE >= 2)
-	CALL	PC_SPACE
-	CALL	PRTHEXWORDHL
-	PRTS(" BYTES$")
-#ENDIF
 ;
 	RET
 ;
+; WAIT FOR SCSI BUS TO BECOME READY WITH A TIMEOUT.
 ;
-;
-IMM_WAITBUSY:
-	LD	HL,500			; NORMAL TIMEOUT COUNTER
-;
-IMM_WAITBUSY_HL:			; VARIABLE TIMEOUT ENTRY
-	LD	A,$0C
-	CALL	IMM_WRITECTRL
-;
-IMM_WAITBUSY2:
+IMM_WAITLOOP:
 	CALL	IMM_READSTATUS
 	BIT	7,A
-	RET	NZ			; IF SET, MOVE ON
+	RET	NZ			; DONE, STATUS IN A
 	DEC	HL
 	LD	A,H
 	OR	L
-	; TODO: IMPLEMENT TIMEOUT!!!
-	;JP	Z,IMM_CMD_TIMEOUT	; TIMEOUT
-	JR	IMM_WAITBUSY2
+	RET	Z			; TIMEOUT
+	JR	IMM_WAITLOOP
 ;
+IMM_WAIT:
+	LD	HL,500			; GOOD VALUE???
+	LD	A,$0C
+	CALL	IMM_WRITECTRL
+	CALL	IMM_WAITLOOP
+	JP	Z,IMM_CMD_TIMEOUT	; HANDLE TIMEOUT
+	PUSH	AF
+	LD	A,$04
+	CALL	IMM_WRITECTRL
+	POP	AF
+	AND	$B8
+	RET				; RETURN W/ RESULT IN A
 ;
+; MAX OBSERVED IMM_WAITLOOP ITERATIONS IS $0116B3
 ;
-IMM_WAITDONE:
-	LD	HL,500			; NORMAL TIMEOUT COUNTER
+IMM_LONGWAIT:
+	LD	B,3			; VALUE???
+	LD	A,$0C
+	CALL	IMM_WRITECTRL
+IMM_LONGWAIT1:
+	LD	HL,0
+	CALL	IMM_WAITLOOP
+	JR	NZ,IMM_LONGWAIT2	; HANDLE SUCCESS
+	DJNZ	IMM_LONGWAIT1		; LOOP TILL COUNTER EXHAUSTED
+	JP	IMM_CMD_TIMEOUT		; HANDLE TIMEOUT
 ;
-IMM_WAITDONE_HL:			; VARIABLE TIMEOUT ENTRY
-	CALL	IMM_WAITBUSY_HL
-	AND	$B8
+IMM_LONGWAIT2:
 	PUSH	AF
 	LD	A,$04
 	CALL	IMM_WRITECTRL
-	POP	AF
-	RET
 ;
+#IF 0
+	CALL	PC_GT
+	LD	A,B
+	CALL	PRTHEXBYTE
+	CALL	PC_COLON
+	CALL	PRTHEXWORDHL
+#ENDIF
 ;
+	POP	AF
+	AND	$B8
+	RET				; RETURN W/ RESULT IN A
+;
+; PEROFRM SCSI BUS NEGOTIATION.  REQURIED PRIOR TO DATA READS.
 ;
 IMM_NEGOTIATE:
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nNEGO: $")
 #ENDIF
 	LD	A,$04
@@ -758,29 +796,28 @@ IMM_NEGOTIATE:
 ;
 	POP	AF
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	PC_SPACE
 	CALL	PRTHEXBYTE
 #ENDIF
 ;
 	AND	$20
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	PC_SPACE
 	CALL	PC_GT
 	CALL	PRTHEXBYTE
 #ENDIF
 ;
-	CP	$20
+	CP	$20			; $20 MEANS DATA READY
 	JP	NZ,IMM_CMD_IOERR
 	RET
 ;
-;
+; GET A BYTE OF DATA FROM THE SCSI DEVICE.  THIS IS A NIBBLE READ.
+; BYTE RETURNED IN A.
 ;
 IMM_GETBYTE:
-	CALL	IMM_WAITBUSY
-	LD	A,$04
-	CALL	IMM_WRITECTRL
+	CALL	IMM_WAIT
 	LD	A,$06
 	CALL	IMM_WRITECTRL
 	CALL	IMM_READSTATUS
@@ -802,53 +839,62 @@ IMM_GETBYTE:
 	POP	AF
 	RET
 ;
+; GET A CHUNK OF DATA FROM SCSI BUS.  THIS IS SPECIFICALLY FOR
+; READ PHASE.  IF A LENGTH IS SPECIFIED (NON-ZERO HL), THEN THE
+; DATA IS BURST READ.  IF NO LENGTH SPECIFIED, DATA IS READ AS
+; LONG AS SCSI DEVICE WANTS TO CONTINUE SENDING (NO OVERRUN
+; CHECK IN THIS CASE).
+;
+; THIS IS A NIBBLE READ.
+;
 ; DE=BUFFER
 ; HL=LENGTH (0 FOR VARIABLE)
 ;
 IMM_GETDATA:
+	; BRANCH TO CORRECT ROUTINE
 	LD	A,H
-	OR	L
-	JR	NZ,IMM_GETDATALEN
+	OR	L			; IF ZERO
+	JR	NZ,IMM_GETDATALEN	; DO BURST READ
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nGETDATA:$")
 #ENDIF
 ;
 IMM_GETDATA1:
-	PUSH	HL
-	CALL	IMM_WAITDONE
-	POP	HL
-	CP	$98
-	JR	NZ,IMM_GETDATA2
+	PUSH	HL			; SAVE BYTE COUNTER
+	CALL	IMM_WAIT		; WAIT FOR BUS READY
+	POP	HL			; RESTORE BYTE COUNTER
+	CP	$98			; CHECK FOR READ PHASE
+	JR	NZ,IMM_GETDATA2		; IF NOT, ASSUME WE ARE DONE
 	LD	A,$04
 	CALL	IMM_WRITECTRL
 	LD	A,$06
 	CALL	IMM_WRITECTRL
-	CALL	IMM_READSTATUS
-	AND	$F0
-	RRCA
+	CALL	IMM_READSTATUS		; GET FIRST NIBBLE
+	AND	$F0			; ISOLATE BITS
+	RRCA				; AND SHIFT TO LOW NIBBLE
 	RRCA
 	RRCA
 	RRCA
-	PUSH 	AF
+	PUSH 	AF			; SAVE WORKING VALUE
 	LD	A,$05
 	CALL	IMM_WRITECTRL
-	CALL	IMM_READSTATUS
-	AND	$F0
-	POP	BC
-	OR	B
-	LD	(DE),A
-	INC	DE
-	INC	HL
+	CALL	IMM_READSTATUS		; GET SECOND NIBBLE
+	AND	$F0			; ISOLATE BITS
+	POP	BC			; RECOVER LOW NIBBLE
+	OR	B			; COMBINE
+	LD	(DE),A			; AND SAVE THE FULL BYTE VALUE
+	INC	DE			; NEXT BUFFER POS
+	INC	HL			; INCREMENT BYTES COUNTER
 	LD	A,$04
 	CALL	IMM_WRITECTRL
 	LD	A,$0C
 	CALL	IMM_WRITECTRL
-	JR	IMM_GETDATA1
+	JR	IMM_GETDATA1		; LOOP TILL DONE
 ;
 IMM_GETDATA2:
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	PC_SPACE
 	CALL	PRTHEXWORDHL
 	PRTS(" BYTES$")
@@ -858,7 +904,7 @@ IMM_GETDATA2:
 ;
 IMM_GETDATALEN:
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nGETDLEN:$")
 	CALL	PC_SPACE
 	CALL	PRTHEXWORDHL
@@ -870,31 +916,39 @@ IMM_GETDATALEN:
 IMM_GETDATALEN1:
 	LD	A,$06
 	CALL	IMM_WRITECTRL
-	CALL	IMM_READSTATUS
-	AND	$F0
-	RRCA
+	CALL	IMM_READSTATUS		; GET FIRST NIBBLE
+	AND	$F0			; ISOLATE BITS
+	RRCA				; MOVE TO LOW NIBBLE
 	RRCA
 	RRCA
 	RRCA
-	PUSH 	AF
+	PUSH 	AF			; SAVE WORKING VALUE
 	LD	A,$05
 	CALL	IMM_WRITECTRL
-	CALL	IMM_READSTATUS
-	AND	$F0
-	POP	BC
-	OR	B
-	LD	(DE),A
-	INC	DE
-	DEC	HL
+	CALL	IMM_READSTATUS		; GET SECOND NIBBLE
+	AND	$F0			; ISOLATE BITS
+	POP	BC			; RECOVER FIRST NIBBLE
+	OR	B			; COMBINE
+	LD	(DE),A			; SAVE FINAL BYTE VALUE
+	INC	DE			; NEXT BUFFER POS
+	DEC	HL			; DEC LOOP COUNTER
 	LD	A,$04
 	CALL	IMM_WRITECTRL
-	LD	A,H
+	LD	A,H			; CHECK LOOP COUNTER
 	OR	L
-	JR	NZ,IMM_GETDATALEN1
+	JR	NZ,IMM_GETDATALEN1	; LOOP IF NOT DONE
 	LD	A,$0C
 	CALL	IMM_WRITECTRL
 	RET
 ;
+; PUT A CHUNK OF DATA TO THE SCSI BUS.  THIS IS SPECIFICALLY FOR
+; WRITE PHASE.  IF A LENGTH IS SPECIFIED (NON-ZERO HL), THEN THE
+; DATA IS BURST WRITTEN.  IF NO LENGTH SPECIFIED, DATA IS WRITTEN AS
+; LONG AS SCSI DEVICE WANTS TO CONTINUE RECEIVING (NO OVERRUN
+; CHECK IN THIS CASE).
+;
+; READS ARE DONE AS BYTE PAIRS.  EACH LOOP READS 2 BYTES.
+;
 ; DE=BUFFER
 ; HL=LENGTH (0 FOR VARIABLE)
 ;
@@ -903,37 +957,37 @@ IMM_PUTDATA:
 	OR	L
 	JR	NZ,IMM_PUTDATALEN
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nPUTDATA:$")
 #ENDIF
 ;
 IMM_PUTDATA1:
-	PUSH	HL
-	CALL	IMM_WAITDONE
-	POP	HL
-	CP	$88
-	JR	NZ,IMM_PUTDATA2
+	PUSH	HL			; SAVE BYTE COUNTER
+	CALL	IMM_WAIT		; WAIT FOR BUS READY
+	POP	HL			; RESTORE BYTE COUNTER
+	CP	$88			; CHECK FOR WRITE PHASE
+	JR	NZ,IMM_PUTDATA2		; IF NOT, ASSUME WE ARE DONE
 	LD	A,$04
 	CALL	IMM_WRITECTRL
-	LD	A,(DE)
-	CALL	IMM_WRITEDATA
-	INC	DE
-	INC	HL
+	LD	A,(DE)			; GET NEXT BYTE TO WRITE (FIRST OF PAIR)
+	CALL	IMM_WRITEDATA		; PUT ON BUS
+	INC	DE			; BUMP TO NEXT BUF POS
+	INC	HL			; INCREMENT COUNTER
 	LD	A,$05
 	CALL	IMM_WRITECTRL
-	LD	A,(DE)
-	CALL	IMM_WRITEDATA
-	INC	DE
-	INC	HL
+	LD	A,(DE)			; GET NEXT BYTE TO WRITE (SECOND OF PAIR)
+	CALL	IMM_WRITEDATA		; PUT ON BUS
+	INC	DE			; BUMP TO NEXT BUF POS
+	INC	HL			; INCREMENT COUNTER
 	LD	A,$00
 	CALL	IMM_WRITECTRL
-	JR	IMM_PUTDATA1
+	JR	IMM_PUTDATA1		; LOOP TILL DONE
 ;
 IMM_PUTDATA2:
 	LD	A,$04
 	CALL	IMM_WRITECTRL
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	PC_SPACE
 	CALL	PRTHEXWORDHL
 	PRTS(" BYTES$")
@@ -943,7 +997,7 @@ IMM_PUTDATA2:
 ;
 IMM_PUTDATALEN:
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nPUTDLEN:$")
 	CALL	PC_SPACE
 	CALL	PRTHEXWORDHL
@@ -953,55 +1007,55 @@ IMM_PUTDATALEN:
 	LD	A,$04
 	CALL	IMM_WRITECTRL
 IMM_PUTDATALEN1:
-	LD	A,(DE)
-	CALL	IMM_WRITEDATA
-	INC	DE
-	DEC	HL
+	LD	A,(DE)			; GET NEXT BYTE (FIRST OF PAIR)
+	CALL	IMM_WRITEDATA		; PUT ON BUS
+	INC	DE			; INCREMENT BUF POS
+	DEC	HL			; DEC LOOP COUNTER
 	LD	A,$05
 	CALL	IMM_WRITECTRL
-	LD	A,(DE)
-	CALL	IMM_WRITEDATA
-	INC	DE
-	DEC	HL
+	LD	A,(DE)			; GET NEXT BYTE (SECOND OF PAIR)
+	CALL	IMM_WRITEDATA		; PUT ON BUS
+	INC	DE			; INCREMENT BUF POS
+	DEC	HL			; DEC LOOP COUNTER
 	LD	A,$00
 	CALL	IMM_WRITECTRL
-	LD	A,H
+	LD	A,H			; CHECK LOOP COUNTER
 	OR	L
-	JR	NZ,IMM_PUTDATALEN1
+	JR	NZ,IMM_PUTDATALEN1	; LOOP TILL DONE
 	LD	A,$04
 	CALL	IMM_WRITECTRL
 	RET
 ;
-;
+; READ SCSI COMMAND STATUS
 ;
 IMM_GETSTATUS:
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nSTATUS:$")
 #ENDIF
 ;
-	CALL	IMM_GETBYTE
-	LD	(IMM_CMDSTAT),A
+	CALL	IMM_GETBYTE		; GET ONE BYTE
+	LD	(IMM_CMDSTAT),A		; SAVE AS FIRST STATUS BYTE
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	PC_SPACE
 	CALL	PRTHEXBYTE
 #ENDIF
 ;
-	CALL	IMM_WAITDONE
-	CP	$B8
-	RET	NZ
-	CALL	IMM_GETBYTE
-	LD	(IMM_CMDSTAT+1),A
+	CALL	IMM_WAIT		; CHECK FOR OPTIONAL SECOND BYTE
+	CP	$B8			; STILL IN STATUS PHASE?
+	RET	NZ			; IF NOT, DONE
+	CALL	IMM_GETBYTE		; ELSE, GET THE SECOND BYTE
+	LD	(IMM_CMDSTAT+1),A	; AND SAVE IT
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	CALL	PC_SPACE
 	CALL	PRTHEXBYTE
 #ENDIF
 ;
 	RET
 ;
-;
+; TERMINATE A BULD READ OPERATION
 ;
 IMM_ENDREAD:
 	LD	A,$04
@@ -1014,26 +1068,37 @@ IMM_ENDREAD:
 	CALL	IMM_WRITECTRL
 	RET
 ;
+; THIS IS THE MAIN SCSI ENGINE.  BASICALLY, IT SELECTS THE DEVICE
+; ON THE BUS, SENDS THE COMMAND, THEN PROCESSES THE RESULT.
+;
 ; HL: COMMAND BUFFER
 ; DE: TRANSFER BUFFER
 ; BC: TRANSFER LENGTH (0=VARIABLE)
 ;
 IMM_RUNCMD:
+	; THERE ARE MANY PLACES NESTED WITHIN THE ROUTINES THAT
+	; ARE CALLED HERE.  HERE WE SAVE THE STACK SO THAT WE CAN
+	; EASILY AND QUICKLY ABORT OUT OF ANY NESTED ROUTINE.
+	; SEE IMM_CMD_ERR BELOW.
 	LD	(IMM_CMDSTK),SP		; FOR ERROR ABORTS
 	LD	(IMM_DSKBUF),DE		; SAVE BUF PTR
 	LD	(IMM_XFRLEN),BC		; SAVE XFER LEN
 	PUSH	HL
-	CALL	IMM_CONNECT
-	CALL	IMM_SELECT
-	CALL	IMM_WAITBUSY
-	POP	DE
-	CALL	IMM_SENDCMD
+	CALL	IMM_CONNECT		; PARALLEL PORT BUS CONNECT
+	CALL	IMM_SELECT		; SELECT TARGET DEVICE
+	CALL	IMM_WAIT		; WAIT TILL READY
+	POP	HL
+	CALL	IMM_SENDCMD		; SEND THE COMMAND
 ;
 IMM_RUNCMD_PHASE:
-	LD	HL,50000		; LONG TIMEOUT HERE
-	CALL	IMM_WAITDONE_HL
-;
-#IF IMMTRACE >= 2)
+	; WAIT FOR THE BUS TO BE READY.  WE USE AN EXTRA LONG WAIT
+	; TIMEOUT HERE BECAUSE THIS IS WHERE WE WILL WAIT FOR LONG
+	; OPERATIONS TO COMPLETE.  IT CAN TAKE SOME TIME IF THE
+	; DEVICE HAS GONE TO SLEEP BECAUSE IT WILL NEED TO WAKE UP
+	; AND SPIN UP BEFORE PROCESSING AN I/O COMMAND.
+	CALL	IMM_LONGWAIT		; WAIT TILL READY
+;
+#IF (IMMTRACE >= 3)
 	PRTS("\r\nPHASE: $")
 	CALL	PRTHEXBYTE
 #ENDIF
@@ -1047,52 +1112,58 @@ IMM_RUNCMD_PHASE:
 	JR	IMM_CMD_IOERR
 ;
 IMM_RUNCMD_WRITE:
-	LD	DE,(IMM_DSKBUF)
+	LD	DE,(IMM_DSKBUF)		; XFER BUFFER
 	LD	HL,(IMM_XFRLEN)		; XFER LENGTH
 	CALL	IMM_PUTDATA		; SEND DATA NOW
-	JR	IMM_RUNCMD_PHASE
+	JR	IMM_RUNCMD_PHASE	; BACK TO DISPATCH
 ;
 IMM_RUNCMD_READ:
-	CALL	IMM_NEGOTIATE
-	CALL	IMM_WAITDONE
+	CALL	IMM_NEGOTIATE		; NEGOTIATE FOR READ
+	CALL	IMM_WAIT		; WAIT TILL READY
 	; CHECK FOR STATUS $98???
-	LD	DE,(IMM_DSKBUF)
+	LD	DE,(IMM_DSKBUF)		; XFER BUFFER
 	LD	HL,(IMM_XFRLEN)		; XFER LENGTH
 	CALL	IMM_GETDATA		; GET THE DATA NOW
-	CALL	IMM_ENDREAD
-	JR	IMM_RUNCMD_PHASE
+	CALL	IMM_ENDREAD		; TERMINATE THE READ
+	JR	IMM_RUNCMD_PHASE	; BACK TO DISPATCH
 ;
 IMM_RUNCMD_END:
-	CALL	IMM_NEGOTIATE
-	CALL	IMM_WAITDONE
+	CALL	IMM_NEGOTIATE		; NEGOTIATE FOR READ (STATUS)
+	CALL	IMM_WAIT		; WAIT TILL READY
 	; CHECK FOR STATUS $B8???
-	CALL	IMM_GETSTATUS
-	CALL	IMM_ENDREAD
-	CALL	IMM_DISCONNECT
+	CALL	IMM_GETSTATUS		; READ STATUS BYTES
+	CALL	IMM_ENDREAD		; TERMINATE THE READ
+	CALL	IMM_DISCONNECT		; PARALLEL PORT BUS DISCONNECT
 	XOR	A			; SIGNAL SUCCESS
 	RET
 ;
 IMM_CMD_IOERR:
-	LD	A,IMM_STIOERR
-	JR	IMM_CMD_ERR
+	LD	A,IMM_STIOERR		; ERROR VALUE TO A
+	JR	IMM_CMD_ERR		; CONTINUE
 ;
 IMM_CMD_TIMEOUT:
-	LD	A,IMM_STTO
-	JR	IMM_CMD_ERR
+	LD	A,IMM_STTO		; ERROR VALUE TO A
+	JR	IMM_CMD_ERR		; CONTINUE
 ;
 IMM_CMD_ERR:
 	LD	SP,(IMM_CMDSTK)		; UNWIND STACK
 	PUSH	AF			; SAVE STATUS
 	;CALL	IMM_RESETPULSE		; CLEAN UP THE MESS???
-	LD	DE,62
+	LD	DE,62			; DELAY AFTER RESET PULSE
 	CALL	VDELAY
-	CALL	IMM_DISCONNECT
-	LD	DE,62
+	CALL	IMM_DISCONNECT		; PARALLEL PORT BUS DISCONNECT
+	LD	DE,62			; DELAY AFTER DISCONNECT
 	CALL	VDELAY
 	POP	AF			; RECOVER STATUS
-	JP	IMM_ERR			; ERROR EXIT
-;
+	JP	IMM_ERR			; NOW DO STANDARD ERR PROCESSING
 ;
+; ERRORS SHOULD GENERALLY NOT CAUSE SCSI PROCESSING TO FAIL.  IF A
+; DEVICE ERROR (I.E., READ ERROR) OCCURS, THEN THE SCSI PROTOCOL WILL
+; PROVIDE ERROR INFORMATION.  THE STATUS RESULT OF THE SCSI COMMAND
+; WILL INDICATE IF AN ERROR OCCURRED.  ADDITIONALLY, IF THE ERROR IS
+; A CHECK CONDITION ERROR, THEN IT IS MANDATORY TO ISSUE A SENSE
+; REQUEST SCSI COMMAND TO CLEAR THE ERROR AND RETRIEVE DETAILED ERROR
+; INFO.
 ;
 IMM_CHKCMD:
 	; SCSI COMMAND COMPLETED, CHECK SCSI CMD STATUS
@@ -1114,7 +1185,7 @@ IMM_CHKCMD1:
 	JP	NZ,IMM_IOERR		; BAIL IF ERROR IN CMD
 ;
 	; REQ SENSE CMD COMPLETED
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	LD	A,16
 	LD	DE,HB_WRKBUF
 	CALL	Z,PRTHEXBUF
@@ -1126,6 +1197,7 @@ IMM_CHKCMD1:
 	JP	NZ,IMM_IOERR		; IF FAILED, GENERAL I/O ERROR
 ;
 	; RETURN RESULT BASED ON REQ SENSE DATA
+	; TODO: WE NEED TO CHECK THE SENSE KEY FIRST!!!
 	LD	A,(HB_WRKBUF+12)	; GET ADDITIONAL SENSE CODE
 	CP	$3A			; NO MEDIA?
 	JP	Z,IMM_NOMEDIA		; IF SO, RETURN NO MEDIA ERR
@@ -1149,65 +1221,73 @@ IMM_INITDEV:
 	LD	C,A			; MOVE TO C FOR I/O
 	LD	A,$82			; CONFIG A OUT, B IN, C OUT
 	OUT	(C),A			; DO IT
-	CALL	DELAY
+	CALL	DELAY			; SHORT DELAY FOR BUS SETTLE
 ;
-	CALL	IMM_DISCONNECT
-	CALL	IMM_CONNECT
-	CALL	IMM_RESETPULSE
-	LD	DE,62
+	CALL	IMM_DISCONNECT		; DISCONNECT FIRST JUST IN CASE
+	CALL	IMM_CONNECT		; NOW CONNECT TO BUS
+	CALL	IMM_RESETPULSE		; ISSUE A SCSI BUS RESET
+	LD	DE,62			; WAIT A BIT
 	CALL	VDELAY
-	CALL	IMM_DISCONNECT
-	LD	DE,62
+	CALL	IMM_DISCONNECT		; AND DISCONNECT FROM BUS
+	LD	DE,62			; WAIT A BIT MORE
 	CALL	VDELAY
 ;
-	LD	B,4
+	; INITIALLY, THE DEVICE MAY REQUIRE MULTIPLE REQUEST SENSE
+	; COMMANDS BEFORE IT WILL ACCEPT I/O COMMANDS.  THIS IS DUE
+	; TO THINGS LIKE BUS RESET NOTIFICATION, MEDIA CHANGE, ETC.
+	; HERE, WE RUN A FEW REQUEST SENSE COMMANDS.  AS SOON AS ONE
+	; INDICATES NO ERRORS, WE CAN CONTINUE.
+	LD	B,4			; TRY UP TO 4 TIMES
 IMM_INITDEV1:
-	PUSH	BC
+	PUSH	BC			; SAVE LOOP COUNTER
 ;
 	; REQUEST SENSE COMMAND
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_SENSE
-	CALL	IMM_RUNCMD
+	LD	DE,HB_WRKBUF		; BUFFER FOR SENSE DATA
+	LD	BC,0			; READ WHATEVER IS SENT
+	LD	HL,IMM_CMD_SENSE	; POINT TO CMD BUFFER
+	CALL	IMM_RUNCMD		; RUN THE SCSI ENGINE
 	JR	NZ,IMM_INITDEV2		; CMD PROC ERROR
 ;
 	; CHECK CMD STATUS
 	LD	A,(IMM_CMDSTAT)		; GET STATUS BYTE
 	OR	A			; SET FLAGS
-	JR	NZ,IMM_INITDEV2		; BAD CMD STATUS
+	JR	NZ,IMM_INITDEV2		; IF ERROR, LOOP
 ;
-#IF IMMTRACE >= 2)
+#IF (IMMTRACE >= 3)
 	LD	A,16
 	LD	DE,HB_WRKBUF
 	CALL	PRTHEXBUF
 #ENDIF
 ;
 	; CHECK SENSE KEY
-	LD	A,(HB_WRKBUF + 2)
-	OR	A
+	LD	A,(HB_WRKBUF + 2)	; GET SENSE KEY
+	OR	A			; SET FLAGS
 ;
 IMM_INITDEV2:
-	POP	BC
+	POP	BC			; RESTORE LOOP COUNTER
 	JR	Z,IMM_INITDEV3		; IF NO ERROR, MOVE ON
 	DJNZ	IMM_INITDEV1		; TRY UNTIL COUNTER EXHAUSTED
-	JP	IMM_IOERR		; HANDLE ERROR
+	JP	IMM_IOERR		; BAIL OUT WITH ERROR
 ;
 IMM_INITDEV3:
 	; READ & RECORD DEVICE CAPACITY
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_RDCAP
-	CALL	IMM_RUNCMD
-	CALL	Z,IMM_CHKCMD
-	RET	NZ			; MEDIA PROBLEM
-;
-#IF IMMTRACE >= 2)
+	LD	DE,HB_WRKBUF		; BUFFER TO CAPACITY RESPONSE
+	LD	BC,0			; READ WHATEVER IS SENT
+	LD	HL,IMM_CMD_RDCAP	; POINT TO READ CAPACITY CMD
+	CALL	IMM_RUNCMD		; RUN THE SCSI ENGINE
+	CALL	Z,IMM_CHKCMD		; CHECK AND RECORD AND ERRORS
+	RET	NZ			; BAIL ON ON ERROR
+;
+#IF (IMMTRACE >= 3)
 	LD	A,8
 	LD	DE,HB_WRKBUF
 	CALL	PRTHEXBUF
 #ENDIF
 ;
-	; INCREMENT, BIG->LITTLE ENDIAN, SAVE
+	; CAPACITY IS RETURNED IN A 4 BYTE, BIG ENDIAN FIELD AND
+	; INDICATES THE LAST LBA VALUE.  WE NEED TO CONVERT THIS TO
+	; LITTLE ENDIAN AND INCREMENT THE VALUE TO MAKE IT A CAPACITY
+	; COUNT INSTEAD OF A LAST LBA VALUE.
 	LD	A,IMM_MEDCAP		; OFFSET IN CFG FOR CAPACITY
 	CALL	LDHLIYA			; POINTER TO HL
 	PUSH	HL			; SAVE IT
@@ -1430,10 +1510,13 @@ IMM_TYPE_MAP:
 IMM_STR_NONE	.DB	"<NOT PRESENT>$"
 IMM_STR_MG014	.DB	"MG014$"
 ;
-; SCSI COMMAND TEMPLATES
+; SCSI COMMAND TEMPLATES (LENGTH PREFIXED)
 ;
+		.DB	6
 IMM_CMD_RW	.DB	$00, $00, $00, $00, $01, $00	; READ/WRITE SECTOR
+		.DB	6
 IMM_CMD_SENSE	.DB	$03, $00, $00, $00, $FF, $00	; REQUEST SENSE DATA
+		.DB	10
 IMM_CMD_RDCAP	.DB	$25, $00, $00, $00, $00, $00, $00, $00, $00, $00 ; READ CAPACITY
 ;
 ; IMM DEVICE CONFIGURATION TABLE
diff --git a/Source/HBIOS/lpt.asm b/Source/HBIOS/lpt.asm
index 7075a7e1..1ee0aab6 100644
--- a/Source/HBIOS/lpt.asm
+++ b/Source/HBIOS/lpt.asm
@@ -372,7 +372,7 @@ LPT_PRTCFG:
 	CALL	PRTHEXBYTE		; PRINT BASE PORT
 
 	; PRINT THE LPT TYPE
-	CALL	PC_SPACE		; FORMATTING
+	PRTS(": MODE=$")		; FORMATTING
 	LD	A,(IY+1)		; GET LPT TYPE BYTE
 	RLCA				; MAKE IT A WORD OFFSET
 	LD	HL,LPT_TYPE_MAP		; POINT HL TO TYPE MAP TABLE
diff --git a/Source/HBIOS/ppa.asm b/Source/HBIOS/ppa.asm
index 529b81b3..e74077de 100644
--- a/Source/HBIOS/ppa.asm
+++ b/Source/HBIOS/ppa.asm
@@ -12,7 +12,8 @@
 ; CREATED BY WAYNE WARTHEN FOR ROMWBW HBIOS.
 ; MUCH OF THE CODE IS DERIVED FROM FUZIX (ALAN COX).
 ;
-; 5/19/2023 WBW - INITIAL RELEASE
+; 5/23/2023 WBW - INITIAL RELEASE
+; 5/26/3023 WBW - CLEAN UP, LED ACTIVITY
 ;
 ;=============================================================================
 ;
@@ -43,20 +44,32 @@
 ;
 ; TODO:
 ;
+; - CLEAN UP WAIT LOOP STUFF
+;
+; - OPTIMIZE READ/WRITE LOOPS
+;
 ; NOTES:
 ;
-;;;;
-;;;; COMMAND BYTES
-;;;;
-;;;PPA_CPPA_NOP		.EQU	$00
-;;;PPA_CPPA_DEVRES		.EQU	$08
-;;;PPA_CPPA_RECAL		.EQU	$10
-;;;PPA_CPPA_READ		.EQU	$20
-;;;PPA_CPPA_WRITE		.EQU	$30
-;;;PPA_CPPA_DEVDIAG	.EQU	$90
-;;;PPA_CPPA_IDPKTDEV	.EQU	$A1
-;;;PPA_CPPA_IDDEV		.EQU	$EC
-;;;PPA_CPPA_SETFEAT	.EQU	$EF
+; - THIS DRIVER IS FOR THE ZIP DRIVE PPA INTERFACE.  IT WILL SIMPLY
+;   FAIL TO EVEN RECOGNIZE A ZIP DRIVE WITH THE OLDER PPA INTERFACE.
+;   THERE DOES NOT SEEM TO BE A WAY TO VISUALLY DETERMINE IF A ZIP
+;   DRIVE IS PPA OR PPA.  SIGH.
+;
+; - THERE ARE SOME HARD CODED TIMEOUT LOOPS IN THE CODE.  THEY ARE
+;   WORKING OK ON A 7 MHZ Z80.  THEY ARE LIKELY TO NEED TWEAKING ON
+;   FASTER CPUS.
+;
+; - THIS DRIVER OPERATES PURELY IN NIBBLE MODE.  I SUSPECT IT IS
+;   POSSIBLE TO USE FULL BYTE MODE (PS2 STYLE), BUT I HAVE NOT
+;   ATTEMPTED IT.
+;
+; - RELATIVE TO ABOVE, THIS BEAST IS SLOW.  IN ADDITION TO THE
+;   NIBBLE MODE READS, THE MG014 ASSIGNS SIGNALS DIFFERENTLY THAN
+;   THE STANDARD IBM PARALLEL PORT WHICH NECESSITATES A BUNCH OF EXTRA
+;   BIT FIDDLING ON EVERY READ.
+;
+; - SOME OF THE DATA TRANSFERS HAVE NO BUFFER OVERRUN CHECKS.  IT IS
+;   ASSUMED SCSI DEVICES WILL SEND/REQUEST THE EXPECTED NUMBER OF BYTES.
 ;
 ; PPA PORT OFFSETS
 ;
@@ -65,6 +78,11 @@ PPA_IOSTAT	.EQU	1		; PORT B, STATUS, IN
 PPA_IOCTRL	.EQU	2		; PORT C, CTRL, OUT
 PPA_IOSETUP	.EQU	3		; PPI SETUP
 ;
+; SCSI UNIT IDS
+;
+PPA_SELF	.EQU	7
+PPA_TGT		.EQU	6
+;
 ; PPA DEVICE STATUS
 ;
 PPA_STOK	.EQU	0
@@ -103,17 +121,8 @@ PPA_INIT1:
 	RET				; AND RETURN
 ;
 PPA_INIT2:
-	; CHECK FOR HARDWARE PRESENCE
-	CALL	PPA_DETECT		; PROBE FOR INTERFACE
-	JP	NZ,PPA_INIT6		; SKIP CFG ENTRY
-;
-	; UPDATE DRIVER RELATIVE UNIT NUMBER IN CONFIG TABLE
-	LD	A,(PPA_DEVNUM)		; GET NEXT UNIT NUM TO ASSIGN
-	LD	(IY+PPA_DEV),A		; UPDATE IT
-	INC	A			; BUMP TO NEXT UNIT NUM TO ASSIGN
-	LD	(PPA_DEVNUM),A		; SAVE IT
-;
-	CALL	PPA_PRTPREFIX		; PRINT DEVICE PREFIX
+	CALL	NEWLINE			; FORMATTING
+	PRTS("PPA:$")			; DRIVER LABEL
 ;
 	PRTS(" IO=0x$")			; LABEL FOR IO ADDRESS
 	LD	A,(IY+PPA_IOBASE)	; GET IO BASE ADDRES
@@ -130,15 +139,32 @@ PPA_INIT2:
 	LD	DE,PPA_STR_MODE_UNK	; MODE LABEL
 PPA_INIT3:
 	CALL	WRITESTR		; DISPLAY MODE
+;
+	; CHECK FOR HARDWARE PRESENCE
+	CALL	PPA_DETECT		; PROBE FOR INTERFACE
+	JR	Z,PPA_INIT4		; IF FOUND, CONTINUE
+	CALL	PC_SPACE		; FORMATTING
+	LD	DE,PPA_STR_NOHW		; NO PPA MESSAGE
+	CALL	WRITESTR		; DISPLAY IT
+	JR	PPA_INIT6		; SKIP CFG ENTRY
 ;
 PPA_INIT4:
-	CALL	PPA_RESET		; RESET THE INTERFACE
+	; UPDATE DRIVER RELATIVE UNIT NUMBER IN CONFIG TABLE
+	LD	A,(PPA_DEVNUM)		; GET NEXT UNIT NUM TO ASSIGN
+	LD	(IY+PPA_DEV),A		; UPDATE IT
+	INC	A			; BUMP TO NEXT UNIT NUM TO ASSIGN
+	LD	(PPA_DEVNUM),A		; SAVE IT
 ;
 	; ADD UNIT TO GLOBAL DISK UNIT TABLE
 	LD	BC,PPA_FNTBL		; BC := FUNC TABLE ADR
 	PUSH	IY			; CFG ENTRY POINTER
 	POP	DE			; COPY TO DE
 	CALL	DIO_ADDENT		; ADD ENTRY TO GLOBAL DISK DEV TABLE
+;
+	CALL	PPA_RESET		; RESET/INIT THE INTERFACE
+;
+	; START PRINTING DEVICE INFO
+	CALL	PPA_PRTPREFIX		; PRINT DEVICE PREFIX
 ;
 	; CHECK FOR BAD STATUS
 	LD	A,(IY+PPA_STAT)		; GET STATUS
@@ -175,9 +201,59 @@ PPA_INIT6:
 ; ON RETURN, ZF SET INDICATES HARDWARE FOUND
 ;
 PPA_DETECT:
+	; INITIALIZE 8255
+	LD	A,(IY+PPA_IOBASE)	; BASE PORT
+	ADD	A,PPA_IOSETUP		; BUMP TO SETUP PORT
+	LD	C,A			; MOVE TO C FOR I/O
+	LD	A,$82			; CONFIG A OUT, B IN, C OUT
+	OUT	(C),A			; DO IT
+	CALL	DELAY			; BRIEF DELAY FOR GOOD MEASURE
+;
+	LD	A,$AA
+	CALL	PPA_WRITEDATA
+	CALL	PPA_DISCONNECT
+	CALL	PPA_CONNECT
+	LD	A,$06
+	CALL	PPA_WRITECTRL
+	CALL	PPA_READSTATUS
+;
+	CALL	PC_SPACE
+	CALL	PRTHEXBYTE
+;
+	AND	$F0
+	CP	$F0
+	JR	NZ,PPA_DETECT_FAIL
+	LD	A,$04
+	CALL	PPA_WRITECTRL
+	CALL	PPA_READSTATUS
+;
+	CALL	PC_SPACE
+	CALL	PRTHEXBYTE
+;
+	AND	$F0
+	CP	$80
+	JR	NZ,PPA_DETECT_FAIL
+	LD	A,$AA
+	CALL	PPA_WRITEDATA
+	LD	A,$0C
+	CALL	PPA_WRITECTRL
+	CALL	PPA_CONNECT
+	LD	A,$40
+	CALL	PPA_WRITEDATA
+	LD	A,$08
+	CALL	PPA_WRITECTRL
+	LD	A,$0C
+	CALL	PPA_WRITECTRL
+	CALL	PPA_DISCONNECT
+;
 	XOR	A			; SIGNAL SUCCESS
 	RET				; AND RETURN
 ;
+PPA_DETECT_FAIL:
+	OR	$FF			; SIGNAL FAILURE
+	RET	NZ
+
+;
 ;=============================================================================
 ; DRIVER FUNCTION TABLE
 ;=============================================================================
@@ -208,12 +284,64 @@ PPA_DEFMED:
 ;
 ;
 PPA_READ:
-	JP	PPA_STNOTSUP		; NOT SUPPORTED
+	CALL	HB_DSKREAD		; HOOK DISK READ CONTROLLER
+	LD	A,SCSI_CMD_READ		; SETUP SCSI READ
+	LD	(PPA_CMD_RW),A		; AND SAVE IT IN SCSI CMD
+	JP	PPA_IO			; DO THE I/O
 ;
 ;
 ;
 PPA_WRITE:
-	JP	PPA_STNOTSUP		; NOT SUPPORTED
+	CALL	HB_DSKREAD		; HOOK DISK WRITE CONTROLLER
+	LD	A,SCSI_CMD_WRITE	; SETUP SCSI WRITE
+	LD	(PPA_CMD_RW),A		; AND SAVE IT IN SCSI CMD
+	JP	PPA_IO			; DO THE I/O
+;
+;
+;
+PPA_IO:
+	LD	(PPA_DSKBUF),HL		; SAVE DISK BUFFER ADDRESS
+	CALL	PPA_CHKERR		; CHECK FOR ERR STATUS AND RESET IF SO
+	JR	NZ,PPA_IO3		; BAIL OUT ON ERROR
+;
+	; SETUP LBA
+	; 3 BYTES, LITTLE ENDIAN -> BIG ENDIAN
+	LD	HL,PPA_CMD_RW+1		; START OF LBA FIELD IN CDB (MSB)
+	LD	A,(IY+PPA_LBA+2)	; THIRD BYTE OF LBA FIELD IN CFG (MSB)
+	LD	(HL),A
+	INC	HL
+	LD	A,(IY+PPA_LBA+1)
+	LD	(HL),A
+	INC	HL
+	LD	A,(IY+PPA_LBA+0)
+	LD	(HL),A
+	INC	HL
+;
+	; DO SCSI IO
+	LD	DE,(PPA_DSKBUF)		; DISK BUFFER TO DE
+	LD	BC,512			; ONE SECTOR, 512 BYTES
+	LD	HL,PPA_CMD_RW		; POINT TO READ/WRITE CMD TEMPLATE
+	CALL	PPA_RUNCMD		; RUN THE SCSI ENGINE
+	CALL	Z,PPA_CHKCMD		; IF EXIT OK, CHECK SCSI RESULTS
+	JR	NZ,PPA_IO2		; IF ERROR, SKIP INCREMENT
+	; INCREMENT LBA
+	LD	A,PPA_LBA		; LBA OFFSET
+	CALL	LDHLIYA			; HL := IY + A, REG A TRASHED
+	CALL	INC32HL			; INCREMENT THE VALUE
+	; INCREMENT DMA
+	LD	HL,IDE_DSKBUF+1		; POINT TO MSB OF BUFFER ADR
+	INC	(HL)			; BUMP DMA BY
+	INC	(HL)			; ... 512 BYTES
+	XOR	A			; SIGNAL SUCCESS
+;
+PPA_IO2:
+PPA_IO3:
+	LD	HL,(PPA_DSKBUF)		; CURRENT DMA TO HL
+	OR	A			; SET FLAGS BASED ON RETURN CODE
+	RET	Z			; RETURN IF SUCCESS
+	LD	A,ERR_IO		; SIGNAL IO ERROR
+	OR	A			; SET FLAGS
+	RET				; AND DONE
 ;
 ;
 ;
@@ -225,6 +353,11 @@ PPA_STATUS:
 ;
 ;
 ;
+PPA_RESET:
+	JP	PPA_INITDEV		; JUST (RE)INIT DEVICE
+;
+;
+;
 PPA_DEVICE:
 	LD	D,DIODEV_PPA		; D := DEVICE TYPE
 	LD	E,(IY+PPA_DEV)		; E := PHYSICAL DEVICE NUMBER
@@ -236,13 +369,12 @@ PPA_DEVICE:
 ;
 ; PPA_GETMED
 ;
-PPA_MEDIA:	
+PPA_MEDIA:
 	LD	A,E			; GET FLAGS
 	OR	A			; SET FLAGS
 	JR	Z,PPA_MEDIA1		; JUST REPORT CURRENT STATUS AND MEDIA
 ;
-	;CALL	PPA_RESET		; RESET PPA INTERFACE
-	CALL	PPA_INITUNIT		; RE-INITIALIZE UNIT
+	CALL	PPA_RESET		; RESET INCLUDES MEDIA CHECK
 ;
 PPA_MEDIA1:
 	LD	A,(IY+PPA_STAT)		; GET STATUS
@@ -297,11 +429,6 @@ PPA_GEOM:
 ; FUNCTION SUPPORT ROUTINES
 ;=============================================================================
 ;
-PPA_SELF	.EQU	7
-PPA_TGT		.EQU	6
-;
-IMM_TGT		.EQU	6
-;
 ;
 ;
 PPA_DELAY:
@@ -315,79 +442,90 @@ PPA_DELAY:
 ;
 ;
 ;
+PPA_WAITDONE:
+	LD	HL,0			; TIMEOUT COUNTER
+PPA_WAITDONE1:
+	CALL	PPA_READSTATUS
+	AND	$F0
+	BIT	7,A
+	RET	NZ
+	DEC	HL
+	LD	A,H
+	OR	L
+	JP	Z,IMM_CMD_TIMEOUT	; TIMEOUT
+	JR	PPA_WAITDONE1
+;
+; OUTPUT BYTE IN A TO THE DATA PORT
+;
 PPA_WRITEDATA:
-	;PRTS(" D-$")
-	;CALL	PRTHEXBYTE
-
-	LD	C,(IY+PPA_IOBASE)
-	OUT	(C),A
-	CALL	PPA_DELAY
-	RET
+	LD	C,(IY+PPA_IOBASE)	; DATA PORT IS AT IOBASE
+	OUT	(C),A			; WRITE THE BYTE
+	;CALL	DELAY			; IS THIS NEEDED???
+	RET				; DONE
 ;
 ;
 ;
 PPA_WRITECTRL:
-	;PRTS(" C-$")
-	;CALL	PRTHEXBYTE
-
-	XOR	$0B
-
-	;PRTS(">$")
-	;CALL	PRTHEXBYTE
-
-	LD	C,(IY+PPA_IOBASE)
+	; IBM PC INVERTS ALL BUT C2 ON THE BUS, MG014 DOES NOT.
+	; BELOW TRANSLATES FROM IBM -> MG014.	IT ALSO INVERTS THE
+	; MG014 LED SIMPLY TO MAKE IT EASY TO KEEP LED ON DURING
+	; ALL ACTIVITY.
+	XOR	$0B | $80		; HIGH BIT IS MG014 LED
+	LD	C,(IY+PPA_IOBASE)	; GET BASE IO ADDRESS
+	INC	C			; BUMP TO CONTROL PORT
 	INC	C
-	INC	C
-	OUT	(C),A
-	CALL	PPA_DELAY
-	RET
+	OUT	(C),A			; WRITE TO CONTROL PORT
+	;CALL	DELAY			; IS THIS NEEDED?
+	RET				; DONE
 ;
+; READ THE PARALLEL PORT INPUT LINES (STATUS) AND MAP SIGNALS FROM
+; MG014 TO IBM STANDARD.  NOTE POLARITY CHANGE REQUIRED FOR BUSY.
 ;
+; 	MG014		IBM PC
+;	--------	--------
+;	0: /ACK		6: /ACK
+;	1: BUSY		7: /BUSY
+;	2: POUT		5: POUT
+;	3: SEL		4: SEL
+;	4: /ERR		3: /ERR
 ;
 PPA_READSTATUS:
-	LD	C,(IY+PPA_IOBASE)
-	INC	C
-	IN	A,(C)
-	
-	;PRTS(" I-$")
-	;CALL	PRTHEXBYTE
-	
+	LD	C,(IY+PPA_IOBASE)	; IOBASE TO C
+	INC	C			; BUMP TO STATUS PORT
+	IN	A,(C)			; READ IT
 	LD	C,0			; INIT RESULT
-;	
-	BIT	0,A			; ACK = $01
+;
+	; SHUFFLE BITS
+	BIT	0,A			; 0: /ACK
 	JR	Z,PPA_READSTATUS1
-	SET	6,C			; $40
+	SET	6,C			; 6: /ACK
 ;
 PPA_READSTATUS1:
-;	
-	BIT	1,A			; BUSY = $02
-	JR	NZ,PPA_READSTATUS2
-	SET	7,C			; $80
+;
+	BIT	1,A			; 1: BUSY
+	JR	NZ,PPA_READSTATUS2	; POLARITY CHANGE!
+	SET	7,C			; 7: /BUSY
 ;
 PPA_READSTATUS2:
-;	
-	BIT	2,A			; PAPER = $04
+;
+	BIT	2,A			; 2: POUT
 	JR	Z,PPA_READSTATUS3
-	SET	5,C			; $20
+	SET	5,C			; 5: POUT
 ;
 PPA_READSTATUS3:
-;	
-	BIT	3,A			; SELECT = $08
+;
+	BIT	3,A			; 3: SEL
 	JR	Z,PPA_READSTATUS4
-	SET	4,C			; $10
+	SET	4,C			; 4: SEL
 ;
 PPA_READSTATUS4:
-;	
-	BIT	4,A			; FAULT = $10
+;
+	BIT	4,A			; 4: /ERR
 	JR	Z,PPA_READSTATUS5
-	SET	3,C			; $08
+	SET	3,C			; 3: /ERR
 ;
 PPA_READSTATUS5:
-	LD	A,C
-	
-	;PRTS(">$")
-	;CALL	PRTHEXBYTE
-	
+	LD	A,C			; RESULT TO A
 	RET
 ;
 ;
@@ -423,7 +561,6 @@ PPA_CPULSE:
 ;
 ;
 PPA_CONNECT:
-	CALL	NEWLINE
 	LD	A,$00
 	CALL	PPA_CPULSE
 	LD	A,$3C
@@ -436,108 +573,7 @@ PPA_CONNECT:
 ;
 ;
 ;
-IMM_CPP:
-	;CALL	NEWLINE
-	PUSH	AF
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	LD	A,$AA
-	CALL	PPA_WRITEDATA
-	LD	A,$55
-	CALL	PPA_WRITEDATA
-	LD	A,$00
-	CALL	PPA_WRITEDATA
-	LD	A,$FF
-	CALL	PPA_WRITEDATA
-	CALL	PPA_READSTATUS
-	AND	$B8
-	LD	(IMM_S1),A
-	LD	A,$87
-	CALL	PPA_WRITEDATA
-	CALL	PPA_READSTATUS
-	AND	$B8
-	LD	(IMM_S2),A
-	LD	A,$78
-	CALL	PPA_WRITEDATA
-	CALL	PPA_READSTATUS
-	AND	$38
-	LD	(IMM_S3),A
-	POP	AF
-	CALL	PPA_WRITEDATA
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	LD	A,$0D
-	CALL	PPA_WRITECTRL
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	LD	A,$FF
-	CALL	PPA_WRITEDATA
-
-	; CONNECT: S1=$B8 S2=$18 S3=$30
-	; DISCONNECT: S1=$B8 S2=$18 S3=$38
-
-	PRTS("\r\nCPP: S1=$")
-	LD	A,(IMM_S1)
-	CALL	PRTHEXBYTE
-	PRTS(" S2=$")
-	LD	A,(IMM_S2)
-	CALL	PRTHEXBYTE
-	PRTS(" S3=$")
-	LD	A,(IMM_S3)
-	CALL	PRTHEXBYTE
-
-	XOR	A		; ASSUME SUCCESS FOR NOW
-	RET
-;
-IMM_S1	.DB	0
-IMM_S2	.DB	0
-IMM_S3	.DB	0
-;
-;
-;
-IMM_CONNECT:
-	LD	A,$E0
-	CALL	IMM_CPP
-	LD	A,$30
-	CALL	IMM_CPP
-	LD	A,$E0
-	CALL	IMM_CPP
-	RET
-;
-;
-;
-IMM_DISCONNECT:
-	LD	A,$30
-	CALL	IMM_CPP
-	RET
-;
-;
-;
-IMM_RESETPULSE:
-	;CALL	NEWLINE
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	LD	A,$40
-	CALL	PPA_WRITEDATA
-	CALL	DELAY
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	LD	A,$0D
-	CALL	PPA_WRITECTRL
-	CALL	DELAY
-	CALL	DELAY
-	CALL	DELAY
-	CALL	DELAY
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	RET
-;
-;
-;
 PPA_DISCONNECT:
-	;CALL	NEWLINE
 	LD	A,$00
 	CALL	PPA_DPULSE
 	LD	A,$3C
@@ -548,6 +584,7 @@ PPA_DISCONNECT:
 	CALL	PPA_DPULSE
 	RET
 ;
+; SCSI SELECT PROCESS
 ;
 ;
 PPA_SELECT:
@@ -574,700 +611,95 @@ PPA_SELECT1:
 	RET	Z			; TIMEOUT
 	JR	PPA_SELECT1
 ;
+; SEND SCSI CMD BYTE STRING.  AT ENTRY, HL POINTS TO START OF
+; COMMAND BYTES.  THE LENGTH OF THE COMMAND STRING MUST PRECEED
+; THE COMMAND BYTES (HL - 1).
 ;
+; NOTE THAT DATA IS SENT AS BYTE PAIRS!  EACH LOOP SENDS 2 BYTES.
+; DATA OUTPOUT IS BURSTED (NO CHECK FOR BUSY).  SEEMS TO WORK FINE.
 ;
-IMM_SELECT:
-	PRTS("\r\nSELECT: $")
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
+PPA_SENDCMD:
+	JP	PPA_ERR			; NOW DO STANDARD ERR PROCESSING
 ;
-	LD	HL,500			; TIMEOUT COUNTER
+; THIS IS THE MAIN SCSI ENGINE.  BASICALLY, IT SELECTS THE DEVICE
+; ON THE BUS, SENDS THE COMMAND, THEN PROCESSES THE RESULT.
 ;
-IMM_SELECT1:
-	CALL	PPA_READSTATUS
-	AND	$08
-	JR	Z,IMM_SELECT2		; IF CLEAR, MOVE ON
-	DEC	HL
-	LD	A,H
-	OR	L
-	JP	Z,IMM_CMD_TIMEOUT	; TIMEOUT
-	JR	IMM_SELECT1
+; HL: COMMAND BUFFER
+; DE: TRANSFER BUFFER
+; BC: TRANSFER LENGTH (0=VARIABLE)
 ;
-IMM_SELECT2:
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	LD	A,$80 | (1 << IMM_TGT)
-	CALL	PPA_WRITEDATA
-	CALL	DELAY
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-
-	CALL	PPA_READSTATUS
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
-
-	LD	A,$0D
-	CALL	PPA_WRITECTRL
-
-	CALL	PPA_READSTATUS
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
+PPA_RUNCMD:
+	JP	PPA_ERR			; NOW DO STANDARD ERR PROCESSING
 ;
-	LD	HL,500			; TIMEOUT COUNTER
+; ERRORS SHOULD GENERALLY NOT CAUSE SCSI PROCESSING TO FAIL.  IF A
+; DEVICE ERROR (I.E., READ ERROR) OCCURS, THEN THE SCSI PROTOCOL WILL
+; PROVIDE ERROR INFORMATION.  THE STATUS RESULT OF THE SCSI COMMAND
+; WILL INDICATE IF AN ERROR OCCURRED.  ADDITIONALLY, IF THE ERROR IS
+; A CHECK CONDITION ERROR, THEN IT IS MANDATORY TO ISSUE A SENSE
+; REQUEST SCSI COMMAND TO CLEAR THE ERROR AND RETRIEVE DETAILED ERROR
+; INFO.
 ;
-IMM_SELECT3:
-	CALL	PPA_READSTATUS
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
-	AND	$08
-	JR	NZ,IMM_SELECT4		; IF CLEAR, MOVE ON
-	DEC	HL
-	LD	A,H
-	OR	L
-	JP	Z,IMM_CMD_TIMEOUT	; TIMEOUT
-	JR	IMM_SELECT3
+PPA_CHKCMD:
+	; SCSI COMMAND COMPLETED, CHECK SCSI CMD STATUS
+	LD	A,(PPA_CMDSTAT)		; GET STATUS BYTE
+	OR	A			; SET FLAGS
+	RET	Z			; IF ZERO, ALL GOOD, DONE
+;
+	; DO WE HAVE A CHECK CONDITION?
+	CP	2			; CHECK CONDITION RESULT?
+	JR	Z,PPA_CHKCMD1		; IF SO, REQUEST SENSE
+	JP	PPA_IOERR		; ELSE, GENERAL I/O ERROR
+;
+PPA_CHKCMD1:
+	; USE REQUEST SENSE CMD TO GET ERROR DETAILS
+	LD	DE,HB_WRKBUF		; PUT DATA IN WORK BUF
+	LD	BC,0			; VARIABLE LENGTH REQUEST
+	LD	HL,PPA_CMD_SENSE	; REQUEST SENSE CMD
+	CALL	PPA_RUNCMD		; DO IT
+	JP	NZ,PPA_IOERR		; BAIL IF ERROR IN CMD
+;
+	; REQ SENSE CMD COMPLETED
+#IF (PPATRACE >= 3)
+	LD	A,16
+	LD	DE,HB_WRKBUF
+	CALL	Z,PRTHEXBUF
+#ENDIF
 ;
-IMM_SELECT4:
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
+	; CHECK SCSI CMD STATUS
+	LD	A,(PPA_CMDSTAT)		; GET STATUS BYTE
+	OR	A			; SET FLAGS
+	JP	NZ,PPA_IOERR		; IF FAILED, GENERAL I/O ERROR
 ;
-	XOR	A
-	RET
+	; RETURN RESULT BASED ON REQ SENSE DATA
+	; TODO: WE NEED TO CHECK THE SENSE KEY FIRST!!!
+	LD	A,(HB_WRKBUF+12)	; GET ADDITIONAL SENSE CODE
+	CP	$3A			; NO MEDIA?
+	JP	Z,PPA_NOMEDIA		; IF SO, RETURN NO MEDIA ERR
+	JP	PPA_IOERR		; ELSE GENERAL I/O ERR
 ;
+; CHECK CURRENT DEVICE FOR ERROR STATUS AND ATTEMPT TO RECOVER
+; VIA RESET IF DEVICE IS IN ERROR.
 ;
+PPA_CHKERR:
+	LD	A,(IY+PPA_STAT)		; GET STATUS
+	OR	A			; SET FLAGS
+	CALL	NZ,PPA_RESET		; IF ERROR STATUS, RESET BUS
+	RET
 ;
-IMM_SENDCMD:
-	; TODO: USE PUTDATA ROUTINE???
-	; TODO: CHECK BUSY???
-	PRTS("\r\nSENDCMD:$")
-	LD	A,$04
-	CALL	PPA_WRITECTRL
+; (RE)INITIALIZE DEVICE
 ;
-	LD	HL,IMM_CMD
-	LD	B,6
+PPA_INITDEV:
+	; INITIALIZE 8255
+	LD	A,(IY+PPA_IOBASE)	; BASE PORT
+	ADD	A,PPA_IOSETUP		; BUMP TO SETUP PORT
+	LD	C,A			; MOVE TO C FOR I/O
+	LD	A,$82			; CONFIG A OUT, B IN, C OUT
+	OUT	(C),A			; DO IT
+	CALL	DELAY			; SHORT DELAY FOR BUS SETTLE
 ;
-IMM_SENDCMD1:
-	LD	A,(HL)
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
-	CALL	PPA_WRITEDATA
-	INC	HL
-	DEC	B
-	LD	A,$05
-	CALL	PPA_WRITECTRL
-	LD	A,(HL)
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
-	CALL	PPA_WRITEDATA
-	INC	HL
-	LD	A,$00
-	CALL	PPA_WRITECTRL
-	DJNZ	IMM_SENDCMD1
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-;
-	CALL	PPA_READSTATUS
-	CALL	PC_SPACE
-	CALL	PC_GT
-	CALL	PRTHEXBYTE
-	RET
-;
-;
-;
-IMM_WAITBUSY:
-	LD	HL,500			; NORMAL TIMEOUT COUNTER
-;
-IMM_WAITBUSY_HL:			; VARIABLE TIMEOUT ENTRY
-	;PRTS("\r\nWAITB: $")
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-;
-IMM_WAITBUSY2:
-	CALL	PPA_READSTATUS
-	BIT	7,A
-	RET	NZ			; IF SET, MOVE ON
-	DEC	HL
-	LD	A,H
-	OR	L
-	JP	Z,IMM_CMD_TIMEOUT	; TIMEOUT
-	JR	IMM_WAITBUSY2
-;
-;
-;
-IMM_WAITDONE:
-	LD	HL,500			; NORMAL TIMEOUT COUNTER
-;
-IMM_WAITDONE_HL:			; VARIABLE TIMEOUT ENTRY
-	CALL	IMM_WAITBUSY_HL
-	AND	$B8
-	PUSH	AF
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	POP	AF
-	RET
-;
-;
-;
-IMM_NEGOTIATE:
-	; TODO: REVIEW TIMING DELAYS!!!
-	PRTS("\r\nNEGO: $")
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	CALL	DELAY
-	LD	A,$00
-	CALL	PPA_WRITEDATA
-	CALL	DELAY
-	CALL	DELAY
-	CALL	DELAY
-	CALL	DELAY
-	LD	A,$06
-	CALL	PPA_WRITECTRL
-	CALL	DELAY
-	CALL	PPA_READSTATUS
-	PUSH	AF			; SAVE RESULT
-	CALL	DELAY
-	LD	A,$07
-	CALL	PPA_WRITECTRL
-	CALL	DELAY
-	LD	A,$06
-	CALL	PPA_WRITECTRL
-;
-	POP	AF
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
-	AND	$20
-	CALL	PC_SPACE
-	CALL	PC_GT
-	CALL	PRTHEXBYTE
-	CP	$20
-	JP	NZ,IMM_CMD_IOERR
-	RET
-;
-;
-;
-PPA_WAITDONE:
-	LD	HL,0			; TIMEOUT COUNTER
-PPA_WAITDONE1:
-	CALL	PPA_READSTATUS
-	AND	$F0
-	BIT	7,A
-	RET	NZ
-	DEC	HL
-	LD	A,H
-	OR	L
-	JP	Z,IMM_CMD_TIMEOUT	; TIMEOUT
-	JR	PPA_WAITDONE1
-;
-;
-;
-IMM_GETBYTE:
-	CALL	IMM_WAITBUSY
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	LD	A,$06
-	CALL	PPA_WRITECTRL
-	CALL	PPA_READSTATUS
-	AND	$F0
-	RRCA
-	RRCA
-	RRCA
-	RRCA
-	PUSH 	AF
-	LD	A,$05
-	CALL	PPA_WRITECTRL
-	CALL	PPA_READSTATUS
-	AND	$F0
-	POP	HL
-	OR	H
-	PUSH	AF
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	POP	AF
-	RET
-;
-; DE=BUFFER
-; HL=LENGTH (0 FOR VARIABLE)
-;
-IMM_GETDATA:
-	LD	A,H
-	OR	L
-	JR	NZ,IMM_GETDATALEN
-	PRTS("\r\nGETDATA:$")
-IMM_GETDATA1:
-	PUSH	HL
-	CALL	IMM_WAITDONE
-	POP	HL
-	CP	$98
-	JR	NZ,IMM_GETDATA2
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	LD	A,$06
-	CALL	PPA_WRITECTRL
-	CALL	PPA_READSTATUS
-	AND	$F0
-	RRCA
-	RRCA
-	RRCA
-	RRCA
-	PUSH 	AF
-	LD	A,$05
-	CALL	PPA_WRITECTRL
-	CALL	PPA_READSTATUS
-	AND	$F0
-	POP	BC
-	OR	B
-	LD	(DE),A
-	INC	DE
-	INC	HL
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	JR	IMM_GETDATA1
-;
-IMM_GETDATA2:
-	CALL	PC_SPACE
-	CALL	PRTHEXWORDHL
-	PRTS(" BYTES$")
-	RET
-;
-IMM_GETDATALEN:
-	PRTS("\r\nGETDLEN:$")
-	CALL	PC_SPACE
-	CALL	PRTHEXWORDHL
-	PRTS(" BYTES$")
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-IMM_GETDATALEN1:
-	LD	A,$06
-	CALL	PPA_WRITECTRL
-	CALL	PPA_READSTATUS
-	AND	$F0
-	RRCA
-	RRCA
-	RRCA
-	RRCA
-	PUSH 	AF
-	LD	A,$05
-	CALL	PPA_WRITECTRL
-	CALL	PPA_READSTATUS
-	AND	$F0
-	POP	BC
-	OR	B
-	LD	(DE),A
-	INC	DE
-	DEC	HL
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	LD	A,H
-	OR	L
-	JR	NZ,IMM_GETDATALEN1
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	RET
-;
-; DE=BUFFER
-; HL=LENGTH (0 FOR VARIABLE)
-;
-IMM_PUTDATA:
-	LD	A,H
-	OR	L
-	JR	NZ,IMM_PUTDATALEN
-	PRTS("\r\nPUTDATA:$")
-IMM_PUTDATA1:
-	PUSH	HL
-	CALL	IMM_WAITDONE
-	POP	HL
-	CP	$88
-	JR	NZ,IMM_PUTDATA2
-
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	LD	A,(DE)
-	CALL	PPA_WRITEDATA
-	INC	DE
-	INC	HL
-	LD	A,$05
-	CALL	PPA_WRITECTRL
-	LD	A,(DE)
-	CALL	PPA_WRITEDATA
-	INC	DE
-	INC	HL
-	LD	A,$00
-	CALL	PPA_WRITECTRL
-	JR	IMM_PUTDATA1
-;
-IMM_PUTDATA2:
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	CALL	PC_SPACE
-	CALL	PRTHEXWORDHL
-	PRTS(" BYTES$")
-	RET
-;
-IMM_PUTDATALEN:
-	PRTS("\r\nPUTDLEN:$")
-	CALL	PC_SPACE
-	CALL	PRTHEXWORDHL
-	PRTS(" BYTES$")
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-IMM_PUTDATALEN1:
-	LD	A,(DE)
-	CALL	PPA_WRITEDATA
-	INC	DE
-	DEC	HL
-	LD	A,$05
-	CALL	PPA_WRITECTRL
-	LD	A,(DE)
-	CALL	PPA_WRITEDATA
-	INC	DE
-	DEC	HL
-	LD	A,$00
-	CALL	PPA_WRITECTRL
-	LD	A,H
-	OR	L
-	JR	NZ,IMM_PUTDATALEN1
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	RET
-;
-;
-;
-IMM_GETSTATUS:
-	PRTS("\r\nSTATUS:$")
-	CALL	IMM_GETBYTE
-	LD	(IMM_STATUS),A
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
-	CALL	IMM_WAITDONE
-	CP	$B8
-	RET	NZ
-	CALL	IMM_GETBYTE
-	LD	(IMM_STATUS+1),A
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
-	RET
-;
-;
-;
-IMM_ENDREAD:
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	LD	A,$0E
-	CALL	PPA_WRITECTRL
-	LD	A,$04
-	CALL	PPA_WRITECTRL
-	RET
-;
-;
-;
-IMM_RUNCMDX:
-	; COPY CMD BYTES FROM (HL)
-	PUSH	BC
-	PUSH	DE
-	LD	BC,6
-	LD	DE,IMM_CMD
-	LDIR
-	POP	DE
-	POP	BC
-;
-IMM_RUNCMD:
-	LD	(IMM_CMDSTK),SP		; FOR ERROR ABORTS
-	LD	(IMM_DSKBUF),DE		; SAVE BUF PTR
-	LD	(IMM_XFRLEN),BC		; SAVE XFER LEN
-	CALL	IMM_CONNECT
-	CALL	IMM_SELECT
-	CALL	IMM_WAITBUSY
-	CALL	IMM_SENDCMD
-;
-IMM_RUNCMD_LOOP:
-	LD	HL,50000		; LONG TIMEOUT HERE
-	CALL	IMM_WAITDONE_HL
-;
-	PRTS("\r\nCMD$")
-	PRTS("LOOP: $")
-	CALL	PRTHEXBYTE
-;
-	CP	$88
-	JR	Z,IMM_RUNCMD_WRITE
-	CP	$98
-	JR	Z,IMM_RUNCMD_READ
-	CP	$B8
-	JR	Z,IMM_RUNCMD_END
-	JR	IMM_CMD_IOERR
-;
-IMM_RUNCMD_WRITE:
-	LD	DE,(IMM_DSKBUF)
-	LD	HL,(IMM_XFRLEN)		; XFER LENGTH
-	CALL	IMM_PUTDATA		; SEND DATA NOW
-	JR	IMM_RUNCMD_LOOP
-;
-IMM_RUNCMD_READ:
-	CALL	IMM_NEGOTIATE
-	CALL	IMM_WAITDONE
-	; CHECK FOR STATUS $98???
-	LD	DE,(IMM_DSKBUF)
-	LD	HL,(IMM_XFRLEN)		; XFER LENGTH
-	CALL	IMM_GETDATA		; GET THE DATA NOW
-	CALL	IMM_ENDREAD
-	JR	IMM_RUNCMD_LOOP
-;
-IMM_RUNCMD_END:
-	CALL	IMM_NEGOTIATE
-	CALL	IMM_WAITDONE
-	; CHECK FOR STATUS $B8???
-	CALL	IMM_GETSTATUS
-	CALL	IMM_ENDREAD
-	CALL	IMM_DISCONNECT
-	XOR	A			; SIGNAL SUCCESS
-	RET
-;
-IMM_CMD_IOERR:
-	LD	A,PPA_STIOERR
-	JR	IMM_CMD_ERR
-;
-IMM_CMD_TIMEOUT:
-	LD	A,PPA_STTO
-	JR	IMM_CMD_ERR
-;
-IMM_CMD_ERR:
-	LD	SP,(IMM_CMDSTK)		; UNWIND STACK
-	PUSH	AF			; SAVE STATUS
-	CALL	IMM_RESETPULSE		; CLEAN UP THE MESS
-	CALL	IMM_DISCONNECT		; MAKE SURE WE ARE OFF THE BUS
-	POP	AF			; RECOVER STATUS
-	JP	PPA_ERR			; ERROR EXIT
-;
-;=============================================================================
-; HARDWARE INTERFACE ROUTINES
-;=============================================================================
-;
-; RESET ALL DEVICES ON BUS
-;
-PPA_RESET:
-	JP	PPA_INITUNIT
-;
-;
-;
-PPA_INITUNIT:
-	;JP	PPA_INITDEV
-	JP	IMM_INITDEV
-;
-; (RE)INITIALIZE DEVICE
-;
-PPA_INITDEV:
-	; INITIALIZE 8255
-	LD	A,(IY+PPA_IOBASE)	; BASE PORT
-	ADD	A,PPA_IOSETUP		; BUMP TO SETUP PORT
-	LD	C,A			; MOVE TO C FOR I/O
-	LD	A,$82			; CONFIG A OUT, B IN, C OUT
-	OUT	(C),A			; DO IT
-	CALL	DELAY
-	
-	CALL	NEWLINE
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	CALL	DELAY
-;
-	; INITIALIZE PPA INTERFACE
-	CALL	PPA_READSTATUS
-	
-	CALL	NEWLINE
-	LD	A,$AA
-	CALL	PPA_WRITEDATA
-
-	CALL	PPA_DISCONNECT
-
-	CALL	PPA_CONNECT
-
-	CALL	NEWLINE
-	;LD	A,$06
-	LD	A,$0E
-	CALL	PPA_WRITECTRL
-	CALL	PPA_READSTATUS
-	AND	$F0
-	;... CHECK VALUE=$F0
-
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
-
-	CALL	NEWLINE
-	;LD	A,$04
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-	CALL	PPA_READSTATUS
-	AND	$F0
-	;... CHECK VALUE=$80
-
-	CALL	PC_SPACE
-	CALL	PRTHEXBYTE
-
-	CALL	PPA_DISCONNECT
-
-	CALL	NEWLINE
-	LD	A,$AA
-	CALL	PPA_WRITEDATA
-	LD	A,$0C			; ???
-	CALL	NEWLINE
-	CALL	PPA_WRITECTRL
-
-	CALL	PPA_CONNECT
-
-	CALL	NEWLINE
-	LD	A,$40
-	CALL	PPA_WRITEDATA
-	LD	A,$08
-	CALL	PPA_WRITECTRL
-	LD	A,$0C
-	CALL	PPA_WRITECTRL
-
-	CALL	PPA_DISCONNECT
-;
-	JP	PPA_NOMEDIA
-;
-	; RECORD STATUS OK
-	XOR	A			; A := 0 (STATUS = OK)
-	LD	(IY+PPA_STAT),A		; SAVE IT
-;
-	RET				; RETURN, A=0, Z SET
-;
-;
-;
-IMM_INITDEV:
-	; INITIALIZE 8255
-	LD	A,(IY+PPA_IOBASE)	; BASE PORT
-	ADD	A,PPA_IOSETUP		; BUMP TO SETUP PORT
-	LD	C,A			; MOVE TO C FOR I/O
-	LD	A,$82			; CONFIG A OUT, B IN, C OUT
-	OUT	(C),A			; DO IT
-	CALL	DELAY
-;
-	CALL	IMM_CONNECT
-	CALL	IMM_RESETPULSE
-	LD	DE,62
-	CALL	VDELAY
-	CALL	IMM_DISCONNECT
-	LD	DE,62
-	CALL	VDELAY
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_SENSE
-	CALL	IMM_RUNCMDX
-	LD	A,16
-	LD	DE,HB_WRKBUF
-	CALL	Z,PRTHEXBUF
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_SENSE
-	CALL	IMM_RUNCMDX
-	LD	A,16
-	LD	DE,HB_WRKBUF
-	CALL	Z,PRTHEXBUF
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,512
-	LD	HL,IMM_CMD_READ
-	CALL	IMM_RUNCMDX
-	LD	DE,HB_WRKBUF
-	CALL	Z,DUMP_BUFFER
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_SENSE
-	CALL	IMM_RUNCMDX
-	LD	A,16
-	LD	DE,HB_WRKBUF
-	CALL	Z,PRTHEXBUF
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,512
-	LD	HL,IMM_CMD_READ
-	CALL	IMM_RUNCMDX
-	LD	DE,HB_WRKBUF
-	CALL	Z,DUMP_BUFFER
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_SENSE
-	CALL	IMM_RUNCMDX
-	LD	A,16
-	LD	DE,HB_WRKBUF
-	CALL	Z,PRTHEXBUF
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_INQ
-	CALL	IMM_RUNCMDX
-	LD	DE,HB_WRKBUF
-	CALL	Z,DUMP_BUFFER
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_SENSE
-	CALL	IMM_RUNCMDX
-	LD	A,16
-	LD	DE,HB_WRKBUF
-	CALL	Z,PRTHEXBUF
-;
-	LD	DE,HB_WRKBUF
-	;LD	BC,512
-	LD	BC,0
-	LD	HL,IMM_CMD_WRITE
-	CALL	IMM_RUNCMDX
-	LD	DE,HB_WRKBUF
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_SENSE
-	CALL	IMM_RUNCMDX
-	LD	A,16
-	LD	DE,HB_WRKBUF
-	CALL	Z,PRTHEXBUF
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,512
-	LD	HL,IMM_CMD_READ2
-	CALL	IMM_RUNCMDX
-	LD	DE,HB_WRKBUF
-	CALL	DUMP_BUFFER
-;
-	LD	DE,HB_WRKBUF
-	LD	BC,0
-	LD	HL,IMM_CMD_SENSE
-	CALL	IMM_RUNCMDX
-	LD	A,16
-	LD	DE,HB_WRKBUF
-	CALL	PRTHEXBUF
-;
-	JP	PPA_NOMEDIA
-;
-IMM_CMD		.DB	$00, $00, $00, $00, $00, $00	; TEMPLATE
-IMM_CMD_READ	.DB	$08, $00, $00, $00, $01, $00	; READ SECTOR $0000
-IMM_CMD_INQ	.DB	$12, $00, $00, $00, $FF, $00	; INQUIRY
-IMM_CMD_TEST	.DB	$00, $00, $00, $00, $00, $00	; TEST UNIT READY
-IMM_CMD_START	.DB	$1B, $00, $00, $00, $01, $00	; START UNIT
-IMM_CMD_SENSE	.DB	$03, $00, $00, $00, $FF, $00	; REQUEST SENSE DATA
-IMM_CMD_WRITE	.DB	$0A, $00, $F0, $00, $01, $00	; READ SECTOR $F000
-IMM_CMD_READ2	.DB	$08, $00, $F0, $00, $01, $00	; READ SECTOR $F000
-
-;
-; CHECK CURRENT DEVICE FOR ERROR STATUS AND ATTEMPT TO RECOVER
-; VIA RESET IF DEVICE IS IN ERROR.
-;
-PPA_CHKERR:
-	LD	A,(IY+PPA_STAT)		; GET STATUS
-	OR	A			; SET FLAGS
-	CALL	NZ,PPA_RESET		; IF ERROR STATUS, RESET BUS
-	RET
-;
-;=============================================================================
-; ERROR HANDLING AND DIAGNOSTICS
-;=============================================================================
+;=============================================================================
+; ERROR HANDLING AND DIAGNOSTICS
+;=============================================================================
 ;
 ; ERROR HANDLERS
 ;
@@ -1395,7 +827,6 @@ PPA_STR_STTO		.TEXT	"TIMEOUT$"
 PPA_STR_STNOTSUP	.TEXT	"NOT SUPPORTED$"
 PPA_STR_STUNK		.TEXT	"UNKNOWN ERROR$"
 ;
-;;;PPA_STR_NO		.TEXT	"NO$"
 PPA_STR_NOHW		.TEXT	"NOT PRESENT$"
 ;
 PPA_STR_MODE_NONE	.TEXT	"NONE$"
@@ -1406,13 +837,11 @@ PPA_STR_MODE_UNK	.TEXT	"???$"
 ; DATA STORAGE
 ;=============================================================================
 ;
-;;;PPA_DSKBUF	.DW	0		; ACTIVE DISK BUFFER
-;
 PPA_DEVNUM	.DB	0		; TEMP DEVICE NUM USED DURING INIT
-IMM_CMDSTK	.DW	0		; STACK PTR FOR CMD ABORTING
-IMM_DSKBUF	.DW	0		; WORKING DISK BUFFER POINTER
-IMM_XFRLEN	.DW	0		; WORKING TRANSFER LENGTH
-IMM_STATUS	.DB	0, 0		; CMD RESULT STATUS
+PPA_CMDSTK	.DW	0		; STACK PTR FOR CMD ABORTING
+PPA_DSKBUF	.DW	0		; WORKING DISK BUFFER POINTER
+PPA_XFRLEN	.DW	0		; WORKING TRANSFER LENGTH
+PPA_CMDSTAT	.DB	0, 0		; CMD RESULT STATUS
 ;
 PPA_TYPE_MAP:
 		.DW	PPA_STR_NONE
@@ -1421,6 +850,15 @@ PPA_TYPE_MAP:
 PPA_STR_NONE	.DB	"<NOT PRESENT>$"
 PPA_STR_MG014	.DB	"MG014$"
 ;
+; SCSI COMMAND TEMPLATES (LENGTH PREFIXED)
+;
+		.DB	6
+PPA_CMD_RW	.DB	$00, $00, $00, $00, $01, $00	; READ/WRITE SECTOR
+		.DB	6
+PPA_CMD_SENSE	.DB	$03, $00, $00, $00, $FF, $00	; REQUEST SENSE DATA
+		.DB	10
+PPA_CMD_RDCAP	.DB	$25, $00, $00, $00, $00, $00, $00, $00, $00, $00 ; READ CAPACITY
+;
 ; PPA DEVICE CONFIGURATION TABLE
 ;
 PPA_CFG:
diff --git a/Source/HBIOS/ppp.asm b/Source/HBIOS/ppp.asm
index c8cc27d6..ac61f866 100644
--- a/Source/HBIOS/ppp.asm
+++ b/Source/HBIOS/ppp.asm
@@ -904,7 +904,7 @@ PPPSD_GETCSD:
 	CALL	PPP_SNDCMD		; SEND COMMAND
 	RET	NZ			; ABORT ON ERROR
 
-	LD	B,16			; GET 4 BYTES
+	LD	B,16			; GET 16 BYTES
 	LD	HL,PPPSD_CSDBUF
 PPPSD_GETCSD1:
 	CALL	PPP_GETBYTE
diff --git a/Source/HBIOS/std.asm b/Source/HBIOS/std.asm
index f057e926..be353573 100644
--- a/Source/HBIOS/std.asm
+++ b/Source/HBIOS/std.asm
@@ -447,6 +447,16 @@ SPD_UNSUP	.EQU	0		; PLATFORM CAN CHANGE SPEEDS BUT IS UNSUPPORTED
 SPD_HIGH	.EQU	1		; PLATFORM CAN CHANGE SPEED, STARTS HIGH
 SPD_LOW		.EQU	2		; PLATFORM CAN CHANGE SPEED, STARTS LOW
 ;
+; SCSI COMMAND CODES (SHOULD BE IT IT'S OWN FILE)
+;
+SCSI_CMD_READ	.EQU	$08
+SCSI_CMD_INQ	.EQU	$12
+SCSI_CMD_TEST	.EQU	$00
+SCSI_CMD_START	.EQU	$1B
+SCSI_CMD_SENSE	.EQU	$03
+SCSI_CMD_WRITE	.EQU	$0A
+SCSI_CMD_RDCAP	.EQU	$25
+;
 #INCLUDE "build.inc"		; INCLUDE USER CONFIG, ADD VARIANT, TIMESTAMP, & ROMSIZE
 ;
 ; INCLUDE Z180 REGISTER DEFINITIONS
diff --git a/Source/ver.inc b/Source/ver.inc
index 1a5a4399..83cbe21f 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,7 +2,7 @@
 #DEFINE	RMN	3
 #DEFINE	RUP	0
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.3.0-dev.15"
+#DEFINE BIOSVER	"3.3.0-dev.16"
 #define rmj	RMJ
 #define rmn	RMN
 #define rup	RUP
diff --git a/Source/ver.lib b/Source/ver.lib
index d9e32aa6..3f43e883 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	3
 rup	equ	0
 rtp	equ	0
 biosver	macro
-	db	"3.3.0-dev.15"
+	db	"3.3.0-dev.16"
 	endm