From 5dc724785b6287909a22bc1309b8278e861cf873 Mon Sep 17 00:00:00 2001
From: Wayne Warthen <wwarthen@gmail.com>
Date: Sun, 19 Nov 2023 14:48:41 -0800
Subject: [PATCH] Completed CH37x Driver

The ch.asm driver now supports SD Card operations (only possible for CH376).
---
 Source/HBIOS/ch.asm | 387 +++++++++++++++++++-------------------------
 Source/ver.inc      |   2 +-
 Source/ver.lib      |   2 +-
 3 files changed, 166 insertions(+), 225 deletions(-)

diff --git a/Source/HBIOS/ch.asm b/Source/HBIOS/ch.asm
index 46ee3bbf..68c8fe87 100644
--- a/Source/HBIOS/ch.asm
+++ b/Source/HBIOS/ch.asm
@@ -1,5 +1,4 @@
 ;
-;
 ;==================================================================================================
 ; CH375/376 USB/SD DRIVER
 ;==================================================================================================
@@ -19,7 +18,7 @@
 ;    added to the RESET routine when using CH376.
 ;
 ; TODO:
-;  - Implement auto-recovery on error status.
+;  - Implement auto-recovery on error status?
 ;  - !!! Move CH_MODE to config variable !!!
 ;
 ; PORT OFFSETS FROM BASE PORT
@@ -47,6 +46,7 @@ CH_CMD_EXIST	.EQU	$06		; CHECK EXISTS
 CH_CMD_MAXLUN	.EQU	$0A		; GET MAX LUN NUMBER
 CH_CMD_PKTSEC	.EQU	$0B		; SET PACKETS PER SECTOR
 CH_CMD_SETRETRY	.EQU	$0B		; SET RETRIES
+CH_CMD_FILESIZE	.EQU	$0C		; GET FILE SIZE (376)
 CH_CMD_MODE	.EQU	$15		; SET USB MODE
 CH_CMD_TSTCON	.EQU	$16		; TEST CONNECT
 CH_CMD_ABRTNAK	.EQU	$17		; ABORT DEVICE NAK RETRIES
@@ -55,6 +55,7 @@ CH_CMD_RD6	.EQU	$27		; READ USB DATA (375 & 376)
 CH_CMD_RD5	.EQU	$28		; READ USB DATA (375)
 CH_CMD_WR5	.EQU	$2B		; WRITE USB DATA (375)
 CH_CMD_WR6	.EQU	$2C		; WRITE USB DATA (376)
+CH_CMD_WRREQDAT	.EQU	$2D		; WRITE REQUESTED DATA (376)
 CH_CMD_SET_FN	.EQU	$2F		; SET FILENAME (376)
 CH_CMD_DSKMNT	.EQU	$31		; DISK MOUNT
 CH_CMD_FOPEN	.EQU	$32		; FILE OPEN (376)
@@ -143,6 +144,8 @@ CH_INIT2:
 	LD	A,(IY+CH_IOBASE)	; GET IO BASE ADDRES
 	CALL	PRTHEXBYTE		; DISPLAY IT
 ;
+	XOR	A			; UNKNOWN MODE
+	LD	(CH_MODE),A		; SAVE IT
 	;CALL	CH_FLUSH		; FLUSH DEVICE OUTPUT QUEUE
 	CALL	CH_RESET		; FULL CH37X RESET
 	CALL	CH_DETECT		; DETECT CHIP PRESENCE
@@ -363,46 +366,45 @@ CH_GETVER:
 ;
 ; SET MODE TO VALUE IN A
 ; AVOID CHANGING MODES IF CURRENT MODE = NEW MODE
+; THE CH376 DOES NOT SEEM TO MAINTAIN SEPARATE OPERATING CONTEXTS FOR
+; THE USB AND SD DEVICES.  IF BOTH ARE IN OPERATION, THEN A MODE
+; SWITCH REQUIRES A COMPLETE REINITIALIZATION OF THE REQUESTED
+; DEVICE.
 ;
 CH_SETMODE:
-	PUSH	BC
-	PUSH	DE
-	PUSH	HL
-	
+	PUSH	BC			; SAVE BC
+	PUSH	DE			; SAVE DE
+	PUSH	HL			; SAVE HL
 	;PRTS("\r\nSETMODE:$")		; *DEBUG*
-	
-	
 	LD	L,A			; SAVE REQUESTED MODE
 	LD	A,(CH_MODE)		; GET CURRENT MODE
-	
 	;CALL	PC_SPACE		; *DEBUG*
 	;CALL	PRTHEXBYTE		; *DEBUG*
-	
 	CP	L			; COMPARE
 	JR	Z,CH_SETMODE_Z		; IF EQUAL, DONE
 ;
 	; NEED TO CHANGE MODES
 	LD	A,L			; GET REQUESTED MODE
-	CP	CH_MODE_USB
-	JR	Z,CH_SETMODE_USB
-	CP	CH_MODE_SD
-	JR	Z,CH_SETMODE_SD
+	CP	CH_MODE_USB		; USB?
+	JR	Z,CH_SETMODE_USB	; IF SO, DO IT
+	CP	CH_MODE_SD		; SD?
+	JR	Z,CH_SETMODE_SD		; IF SO, DO IT
 	OR	$FF			; SIGNAL ERROR
 	JR	CH_SETMODE_Z		; BAIL OUT
 ;
 CH_SETMODE_USB:
-	CALL	CHUSB_RESET
-	JR	CH_SETMODE_Z
+	CALL	CHUSB_RESET		; FULL USB STACK RESET
+	JR	CH_SETMODE_Z		; MOVE ON
 ;
 CH_SETMODE_SD:
-	CALL	CHSD_RESET
-	JR	CH_SETMODE_Z
+	CALL	CHSD_RESET		; FULL SD STACK RESET
+	JR	CH_SETMODE_Z		; MOVE ON
 ;
 CH_SETMODE_Z:
-	POP	HL
-	POP	DE
-	POP	BC
-	RET
+	POP	HL			; RECOVER HL
+	POP	DE			; RECOVER DE
+	POP	BC			; RECOVER BC
+	RET				; DONE
 ;
 ;
 ;
@@ -742,29 +744,28 @@ CHUSB_RESET1:
 	;CALL	PC_SPACE		; *DEBUG*
 	;CALL	PRTHEXBYTE		; *DEBUG*
 	CP	$14			; SUCCESS?
-	JR	Z,CHUSB_RESET2		; IF SO, CONTINUE
-	;JR	Z,CHUSB_RESET1A		; IF SO, CHECK READY
+	JR	Z,CHUSB_RESET1A		; IF SO, CHECK READY
 	CP	$16			; NO MEDIA
 	JP	Z,CHUSB_NOMEDIA		; HANDLE IT
 	CALL	CH_NAP			; SMALL DELAY
 	DJNZ	CHUSB_RESET1		; LOOP AS NEEDED
 	JP	CHUSB_TO		; HANDLE TIMEOUT
-;;;;
-;;;CHUSB_RESET1A:
-;;;	CALL	CHUSB_DSKRES		; DISK RESET
-;;;	CP	$14			; GOOD?
-;;;	JR	Z,CHUSB_RESET2
-;;;	CALL	CHUSB_DSKRDY		; CHECK IF DISK READY
-;;;	CP	$14			; GOOD?
-;;;	JR	Z,CHUSB_RESET2		; IF SO, MOVE ON
-;;;	DJNZ	CHUSB_RESET1		; KEEP TRYING
+;
+CHUSB_RESET1A:
+	;CALL	CHUSB_DSKRES		; DISK RESET
+	;CP	$14			; GOOD?
+	;JR	Z,CHUSB_RESET2
+	;CALL	CHUSB_DSKRDY		; CHECK IF DISK READY
+	;CP	$14			; GOOD?
+	;JR	Z,CHUSB_RESET2		; IF SO, MOVE ON
+	;DJNZ	CHUSB_RESET1		; KEEP TRYING
 ;
 CHUSB_RESET2:
 	; USE OF CH376 DISK_MOUNT COMMAND SEEMS TO IMPROVE
 	; COMPATIBILITY WITH SOME OLDER USB THUMBDRIVES.
 	LD	A,(IY+CH_TYPE)		; CH37X TYPE?
 	CP	CHTYP_376		; IS CH376?
-	CALL	Z,CHUSB_DSKMNT		; IF SO, ISSUE MOUNT
+	CALL	Z,CHUSB_DSKMNT		; IF SO, TRY MOUNT, IGNORE ERRS
 	;CALL	CHUSB_AUTOSET		; *DEBUG*
 	;CALL	CHUSB_TSTCON		; *DEBUG*
 	;CALL	CHUSB_MAXLUN		; *DEBUG*
@@ -862,28 +863,34 @@ CHUSB_DSKMNT:
 	;CALL	PRTHEXBYTE		; *DEBUG*
 	CP	$14			; SUCCESS?
 	RET	NZ			; ABORT IF NOT
+;
+#IF FALSE
 	CALL	CH_CMD_RD		; SEND READ COMMAND
 	CALL	CH_RD			; GET LENGTH
+	;CALL	PC_SPACE		; *DEBUG*
+	;CALL	PRTHEXBYTE		; *DEBUG*
 	LD	B,A			; LOOP COUNTER
 	LD	HL,HB_WRKBUF		; USE WORK BUFFER FOR DATA
-DSKMNT1:
+CHUSB_DSKMNT1:
 	CALL	CH_RD			; GET A BYTE
 	LD	(HL),A			; SAVE IT
 	INC	HL			; BUMP BUF PTR
-	DJNZ	DSKMNT1			; LOOP FOR ALL DATA
+	DJNZ	CHUSB_DSKMNT1		; LOOP FOR ALL DATA
 ;
 	;LD	DE,HB_WRKBUF		; *DEBUG*
 	;CALL	DUMP_BUFFER		; *DEBUG*
 ;
-	;CALL	CHUSB_PRTPREFIX		; PRINT DEVICE PREFIX
-	;LD	HL,HB_WRKBUF + 8
-	;LD	B,28
-DSKMNT2:
-	;LD	A,(HL)
-	;INC	HL
-	;CALL	COUT
-	;DJNZ	DSKMNT2
+	CALL	CHUSB_PRTPREFIX		; PRINT DEVICE PREFIX
+	LD	HL,HB_WRKBUF + 8
+	LD	B,28
+CHUSB_DSKMNT2:
+	LD	A,(HL)
+	INC	HL
+	CALL	COUT
+	DJNZ	CHUSB_DSKMNT2
+#ENDIF
 ;
+	XOR	A
 	RET
 ;
 ; PERFORM DISK SIZE
@@ -1161,6 +1168,8 @@ CHUSB_STR_STUNK		.TEXT	"UNKNOWN ERROR$"
 ; CH375/376 SD CARD SUB-DRIVER
 ;==================================================================================================
 ;
+#DEFINE	CHSD_IMGFILE "DISK.IMG"
+;
 CHSD_FASTIO	.EQU	TRUE		; USE INIR/OTIR?
 ;
 ; CHUSB DEVICE STATUS
@@ -1315,9 +1324,9 @@ CHSD_READ1:
 	CALL	CH_RD			; GET DATA LENGTH
 	;CALL	PC_SPACE		; *DEBUG*
 	;CALL	PRTHEXBYTE		; *DEBUG*
-
+;
 #IF (CHSD_FASTIO)
-	LD	B,A
+	LD	B,A			; BYTE COUNT TO READ
 	LD	C,(IY+CH_IOBASE)	; BASE PORT
 	INIR				; DO IT FAST
 #ELSE
@@ -1357,54 +1366,55 @@ CHSD_WRITE:
 	CALL	CH_SETMODE		; DO IT
 	JP	NZ,CHSD_CMDERR		; HANDLE ERROR
 ;
-	JP	CHSD_IOERR
-
 	CALL	HB_DSKWRITE		; HOOK HBIOS DISK WRITE SUPERVISOR
 	LD	(CHSD_DSKBUF),HL	; SAVE DISK BUFFER ADDRESS
-	LD	A,CH_CMD_DSKWR		; DISK READ COMMAND
-	CALL	CHSD_RWSTART		; SEND CMD AND LBA
+	CALL	CHSD_RWSTART		; SET LBA OFFSET'
+	RET	NZ
 ;
-	; WRITE THE SECTOR IN 64 BYTE CHUNKS
-	LD	B,8			; 8 CHUNKS OF 64 FOR 512 BYTE SECTOR
-	LD	HL,(CHSD_DSKBUF)	; GET DISK BUF ADR
+	;PRTS("\n\rWRITE:$")		; *DEBUG*
+	LD	A,CH_CMD_BYTEWR		; BYTE WRITE
+	CALL	CH_CMD			; SEND COMMAND
+	LD	A,0			; LSB
+	CALL	CH_WR			; SEND IT
+	LD	A,2			; MSB
+	CALL	CH_WR			; SEND IT
+	CALL	CH_POLL			; GET RESULT
+	;CALL	PC_SPACE		; *DEBUG*
+	;CALL	PRTHEXBYTE		; *DEBUG*
+	CP	$1E			; DATA READY TO GO?
+	JP	NZ,CHSD_IOERR		; HANDLE I/O ERROR
+;
+	LD	HL,(CHSD_DSKBUF)
 CHSD_WRITE1:
-	CALL	CH_POLL			; WAIT FOR DATA READY
-	CP	$1E			; DATA READY TO WRITE
-	;CALL	PC_GT			; *DEBUG*
+	LD	A,CH_CMD_WRREQDAT	; WRITE REQUESTED DATA CMD
+	CALL	CH_CMD			; SEND IT
+	CALL	CH_RD			; GET DATA LENGTH
+	;CALL	PC_SPACE		; *DEBUG*
 	;CALL	PRTHEXBYTE		; *DEBUG*
-	JP	NZ,CHSD_IOERR		; HANDLE IO ERROR
-	CALL	CH_CMD_WR		; SEND WRITE USB DATA CMD
-	LD	A,64			; 64 BYTE CHUNK
-	CALL	CH_WR			; SEND DATA BLOCK LENGTH
 ;
 #IF (CHSD_FASTIO)
-	; WRITE 64 BYTE CHUNK
-	PUSH	BC			; SAVE LOOP CONTROL
-	LD	B,64			; WRITE 64 BYTES
+	LD	B,A			; BYTE COUNT TO WRITE
 	LD	C,(IY+CH_IOBASE)	; BASE PORT
 	OTIR				; DO IT FAST
-	POP	BC			; RESTORE LOOP CONTROL
 #ELSE
-	; BYTE WRITE LOOP
-	PUSH	BC			; SAVE LOOP CONTROL
-	LD	B,64			; WRITE 64 BYTES
+	LD	B,A			; SAVE IT
 CHSD_WRITE2:
-	LD	A,(HL)			; GET NEXT BYTE
+	CALL	CH_WR			; WRITE DATA BYTE
+	LD	(HL),A			; SAVE IN BUFFER
 	INC	HL			; INC BUF PTR
-	CALL	CH_WR			; WRITE NEXT BYTE
-	DJNZ	CHSD_WRITE2		; LOOP AS NEEDED
-	POP	BC			; RESTORE LOOP CONTROL
+	DJNZ	CHSD_WRITE2		; LOOP TILL DONE W/ ALL BYTES
 #ENDIF
 ;
-	; PREPARE FOR NEXT CHUNK
-	LD	A,CH_CMD_DSKWRGO	; CONTINUE DISK READ
+	LD	A,CH_CMD_BYTEWRGO	; BYTE WRITE GO COMMAND
 	CALL	CH_CMD			; SEND IT
-	DJNZ	CHSD_WRITE1		; LOOP TILL DONE
-;
-	; FINAL CHECK FOR COMPLETION & SUCCESS
-	CALL	CH_POLL			; WAIT FOR COMPLETION
-	CP	$14			; SUCCESS?
-	JP	NZ,CHSD_IOERR		; IF NOT, HANDLE ERROR
+	CALL	CH_NAP
+	CALL	CH_POLL			; GET RESULT
+	;CALL	PC_SPACE		; *DEBUG*
+	;CALL	PRTHEXBYTE		; *DEBUG*
+	CP	$1E			; MORE?
+	JR	Z,CHSD_WRITE1		; IF SO, SEND MORE
+	CP	$14			; GOOD FINISH?
+	JP	NZ,CHSD_IOERR		; HANDLE ERROR
 ;
 	; INCREMENT LBA
 	PUSH	HL			; SAVE HL
@@ -1469,30 +1479,6 @@ CHSD_STATUS:
 ;
 CHSD_RESET:
 	;PRTS("\n\rRES SD:$")		; *DEBUG*
-	;CALL	CH_FLUSH		; DISCARD ANY GARBAGE
-	;CALL	CH_RESET		; FULL CH37X RESET
-;;;;
-;;;	; RESET THE BUS
-;;;	LD	A,CH_CMD_MODE		; SET MODE COMMAND
-;;;	CALL	CH_CMD			; SEND IT
-;;;	LD	A,7			; RESET BUS
-;;;	CALL	CH_WR			; SEND IT
-;;;	CALL	CH_NAP			; SMALL WAIT
-;;;	CALL	CH_RD			; GET RESULT
-;;;	CALL	PC_SPACE		; *DEBUG*
-;;;	CALL	PRTHEXBYTE		; *DEBUG*
-;;;	CALL	CH_NAP			; SMALL WAIT
-;;;;
-;;;	; ACTIVATE USB MODE
-;;;	LD	A,CH_CMD_MODE		; SET MODE COMMAND
-;;;	CALL	CH_CMD			; SEND IT
-;;;	LD	A,6			; USB ENABLED, SEND SOF
-;;;	CALL	CH_WR			; SEND IT
-;;;	CALL	CH_NAP			; SMALL WAIT
-;;;	CALL	CH_RD			; GET RESULT
-;;;	;CALL	PC_SPACE		; *DEBUG*
-;;;	;CALL	PRTHEXBYTE		; *DEBUG*
-;;;	CALL	CH_NAP			; SMALL WAIT
 ;
 	; ACTIVATE SD MODE
 	LD	A,CH_CMD_MODE		; SET MODE COMMAND
@@ -1507,70 +1493,18 @@ CHSD_RESET:
 ;
 	LD	A,CH_MODE_SD		; WE ARE NOW IN SD MODE
 	LD	(CH_MODE),A		; SAVE IT
-;;;;
-;;;	; INITIALIZE DISK
-;;;	LD	B,24			; TRY A FEW TIMES
-;;;CHSD_RESET1:
-;;;	PRTS("\n\rDSKINIT:$")		; *DEBUG*
-;;;	LD	A,CH_CMD_DSKINIT	; DISK INIT COMMAND
-;;;	CALL	CH_CMD			; SEND IT
-;;;	LD	DE,10000		; 10000 * 16 = 160US ???
-;;;	LD	DE,20000		; 10000 * 16 = 160US ???
-;;;	LD	DE,12500		; 1250 * 16 = 200US ???
-;;;	CALL	VDELAY			; DELAY
-;;;	CALL	CH_POLL			; WAIT FOR RESULT
-;;;	CALL	PC_SPACE		; *DEBUG*
-;;;	CALL	PRTHEXBYTE		; *DEBUG*
-;;;	CP	$14			; SUCCESS?
-;;;	JR	Z,CHSD_RESET2		; IF SO, CONTINUE
-;;;	;JR	Z,CHSD_RESET1A		; IF SO, CHECK READY
-;;;	CP	$16			; NO MEDIA
-;;;	JP	Z,CHSD_NOMEDIA		; HANDLE IT
-;;;	CALL	CH_NAP			; SMALL DELAY
-;;;	DJNZ	CHSD_RESET1		; LOOP AS NEEDED
-;;;	JP	CHSD_TO			; HANDLE TIMEOUT
-;;;;;;;
-;;;;;;CHSD_RESET1A:
-;;;;;;	CALL	CHSD_DSKRES		; DISK RESET
-;;;;;;	CP	$14			; GOOD?
-;;;;;;	JR	Z,CHSD_RESET2
-;;;;;;	CALL	CHSD_DSKRDY		; CHECK IF DISK READY
-;;;;;;	CP	$14			; GOOD?
-;;;;;;	JR	Z,CHSD_RESET2		; IF SO, MOVE ON
-;;;;;;	DJNZ	CHSD_RESET1		; KEEP TRYING
-;
-CHSD_RESET2:
+;
 	CALL	CHSD_DSKMNT		; MOUNT DISK
 	RET	NZ
-;
-	;CALL	CHSD_AUTOSET		; *DEBUG*
-	;CALL	CHSD_TSTCON		; *DEBUG*
-	;CALL	CHSD_MAXLUN		; *DEBUG*
-	;CALL	CHSD_DSKRDY		; *DEBUG*
-	;CALL	CHSD_DSKINQ		; *DEBUG*
-;;
-	CALL	CHSD_DSKCAP		; GET AND RECORD DISK CAPACITY
-	RET	NZ			; ABORT ON ERROR
 ;
 	; OPEN DISK IMAGE FILE
 	LD	DE,CHSD_FNAME
 	CALL	CHSD_FOPEN
 	RET	NZ
-;;;;
-;;;	; *DEBUG*
-;;;	LD	HL,HB_WRKBUF
-;;;	LD	E,1
-;;;	CALL	CHSD_READ
-;;;;
-;;;;
-;;;	LD	DE,HB_WRKBUF		; *DEBUG*
-;;;	CALL	DUMP_BUFFER		; *DEBUG*
-	
-
-
-
-
-
+;
+	; GET FILESIZE
+	CALL	CHSD_FILESIZE
+	RET	NZ
 ;
 	; SET STATUS AND RETURN
 	XOR	A			; CLEAR STATUS
@@ -1658,72 +1592,39 @@ CHSD_DSKMNT:
 	CALL	CH_POLL			; WAIT FOR RESPONSE
 	;CALL	PC_SPACE		; *DEBUG*
 	;CALL	PRTHEXBYTE		; *DEBUG*
+	CP	$82			; NO DISK?
+	JP	Z,CHSD_NOMEDIA		; HANDLE NO MEDIA ERROR
 	CP	$14			; SUCCESS?
 	JP	NZ,CHSD_CMDERR		; HANDLE ERROR
 ;
-;	CALL	CH_CMD_RD		; SEND READ COMMAND
-;	CALL	CH_RD			; GET LENGTH
-;	;CALL	PC_SPACE		; *DEBUG*
-;	;CALL	PRTHEXBYTE		; *DEBUG*
-;	LD	B,A			; LOOP COUNTER
-;	LD	HL,HB_WRKBUF		; USE WORK BUFFER FOR DATA
-;CHSD_DSKMNT1:
-;	CALL	CH_RD			; GET A BYTE
-;	CALL	PC_SPACE
-;	CALL	PRTHEXBYTE
-;	LD	(HL),A			; SAVE IT
-;	INC	HL			; BUMP BUF PTR
-;	DJNZ	CHSD_DSKMNT1		; LOOP FOR ALL DATA
-;;
-;	;LD	DE,HB_WRKBUF		; *DEBUG*
-;	;CALL	DUMP_BUFFER		; *DEBUG*
-;;
-;	CALL	CHSD_PRTPREFIX		; PRINT DEVICE PREFIX
-;	PRTS(" \"$")
-;	LD	HL,HB_WRKBUF + 8
-;	LD	B,28
-;CHSD_DSKMNT2:
-;	LD	A,(HL)
-;	INC	HL
-;	CALL	COUT
-;	DJNZ	CHSD_DSKMNT2
-;	PRTS("\"$")
+#IF FALSE
+	CALL	CH_CMD_RD		; SEND READ COMMAND
+	CALL	CH_RD			; GET LENGTH
+	;CALL	PC_SPACE		; *DEBUG*
+	;CALL	PRTHEXBYTE		; *DEBUG*
+	LD	B,A			; LOOP COUNTER
+	LD	HL,HB_WRKBUF		; USE WORK BUFFER FOR DATA
+CHSD_DSKMNT1:
+	CALL	CH_RD			; GET A BYTE
+	LD	(HL),A			; SAVE IT
+	INC	HL			; BUMP BUF PTR
+	DJNZ	CHSD_DSKMNT1		; LOOP FOR ALL DATA
 ;
-	XOR	A
-	RET
+	;LD	DE,HB_WRKBUF		; *DEBUG*
+	;CALL	DUMP_BUFFER		; *DEBUG*
 ;
-; PERFORM DISK CAPACITY
+	CALL	CHSD_PRTPREFIX		; PRINT DEVICE PREFIX
+	LD	HL,HB_WRKBUF + 8
+	LD	B,28
+CHSD_DSKMNT2:
+	LD	A,(HL)
+	INC	HL
+	CALL	COUT
+	DJNZ	CHSD_DSKMNT2
+#ENDIF
 ;
-CHSD_DSKCAP:
-	;PRTS("\n\rDSKCAP:$")		; *DEBUG*
-	LD	A,CH_CMD_DSKCAP		; DISK CAPACITY COMMAND
-	CALL	CH_CMD			; SEND IT
-	CALL	CH_POLL			; WAIT FOR RESULT
-	;CALL	PC_SPACE		; *DEBUG*
-	;CALL	PRTHEXBYTE		; *DEBUG*
-	CP	$14			; SUCCESS?
-	JP	NZ,CHSD_CMDERR		; HANDLE CMD ERROR
-	CALL	CH_CMD_RD		; SEND READ USB DATA CMD
-	CALL	CH_RD			; GET RD DATA LEN
-	;CALL	PC_SPACE		; *DEBUG*
-	;CALL	PRTHEXBYTE		; *DEBUG*
-	CP	$04			; MAKE SURE IT IS 8
-	JP	NZ,CHSD_CMDERR		; HANDLE CMD ERROR
-	LD	A,CHSD_MEDCAP		; MEDIA CAPACITY OFFSET
-	CALL	LDHLIYA			; HL := IY + A, REG A TRASHED
-	PUSH	HL			; SAVE ADDRESS
-	CALL	CH_RD
-	LD	L,A
-	CALL	CH_RD
-	LD	H,A
-	CALL	CH_RD
-	LD	E,A
-	CALL	CH_RD
-	LD	D,A
-	POP	BC			; RECOVER ADDRESS TO BC
-	CALL	ST32			; STORE IT
-	XOR	A			; SIGNAL SUCCESS
-	RET				; AND DONE
+	XOR	A
+	RET
 ;
 ; SET FILE NAME
 ;
@@ -1754,10 +1655,48 @@ CHSD_FOPEN:
 	CALL	CH_POLL			; WAIT FOR RESULT
 	;CALL	PC_SPACE		; *DEBUG*
 	;CALL	PRTHEXBYTE		; *DEBUG*
+	CP	$42			; MISSING FILE?
+	JP	Z,CHSD_NOFILE		; HANDLE ERROR
 	CP	$14			; SUCCESS?
-	JP	NZ,CHSD_NOFILE		; HANDLE ERROR
+	JP	NZ,CHSD_IOERR		; HANDLE ERROR
 	RET				; RETURN WITH ZF SET APPROPRIATELY
 ;
+; GET FILE SIZE
+;
+CHSD_FILESIZE:
+	;PRTS("\n\rFSIZE:$")
+	LD	A,CH_CMD_FILESIZE	; FILE SIZE COMMAND
+	CALL	CH_CMD			; SEND IT
+	LD	A,$68			; REQUIRED CMD PARAMETER
+	CALL	CH_WR			; SEND IT
+	CALL	CH_NAP
+	LD	A,CHSD_MEDCAP		; MEDIA CAPACITY OFFSET
+	CALL	LDHLIYA			; HL := IY + A, REG A TRASHED
+	PUSH	HL			; SAVE ADDRESS
+	CALL	CH_RD
+	LD	L,A
+	CALL	CH_RD
+	LD	H,A
+	CALL	CH_RD
+	LD	E,A
+	CALL	CH_RD
+	LD	D,A
+	;CALL	PC_SPACE		; *DEBUG*
+	;CALL	PRTHEX32		; *DEBUG*
+	LD	B,9			; ROTATE 9 BITS FOR DIV 512
+CHSD_FILESIZE1:
+	SRL	D
+	RR	E
+	RR	H
+	RR	L
+	DJNZ	CHSD_FILESIZE1		; LOOP TILL DONE
+	POP	BC			; RECOVER ADDRESS TO BC
+	;CALL	PC_SPACE		; *DEBUG*
+	;CALL	PRTHEX32		; *DEBUG*
+	CALL	ST32			; STORE IT
+	XOR	A			; SIGNAL SUCCESS
+	RET				; AND DONE
+;
 ; ERROR HANDLERS
 ;
 ;
@@ -1853,7 +1792,7 @@ CHSD_PRTPREFIX:
 CHSD_DEVNUM	.DB	0		; TEMP DEVICE NUM USED DURING INIT
 CHSD_DSKBUF	.DW	0
 ;
-CHSD_FNAME	.DB	"/DISK.IMG",0
+CHSD_FNAME	.DB	"/", CHSD_IMGFILE, 0
 ;
 CHSD_STR_ST_MAP:
 	.DW		CHSD_STR_STOK
@@ -1870,5 +1809,7 @@ CHSD_STR_STCMDERR	.TEXT	"COMMAND ERROR$"
 CHSD_STR_STIOERR	.TEXT	"IO ERROR$"
 CHSD_STR_STTO		.TEXT	"TIMEOUT$"
 CHSD_STR_STNOTSUP	.TEXT	"NOT SUPPORTED$"
-CHSD_STR_STNOFILE	.TEXT	"MISSING DISK IMAGE FILE$"
+CHSD_STR_STNOFILE	.TEXT	"MISSING "
+			.TEXT	CHSD_IMGFILE
+			.TEXT	" FILE$"
 CHSD_STR_STUNK		.TEXT	"UNKNOWN ERROR$"
diff --git a/Source/ver.inc b/Source/ver.inc
index 1388bcdf..5017e3bb 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,7 +2,7 @@
 #DEFINE	RMN	4
 #DEFINE	RUP	0
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.4.0-dev.20"
+#DEFINE BIOSVER	"3.4.0-dev.21"
 #define rmj	RMJ
 #define rmn	RMN
 #define rup	RUP
diff --git a/Source/ver.lib b/Source/ver.lib
index 11d4c54a..73600fa8 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	4
 rup	equ	0
 rtp	equ	0
 biosver	macro
-	db	"3.4.0-dev.20"
+	db	"3.4.0-dev.21"
 	endm