Aus KRAUSE 057 -  FDC.PRN

                ;************************************************
                ;	FLOPPY DRIVER MODULE FOR CPM 3.0

Die Parameter werden per MACRO erzeigt.
#
AUS FDC.ASM

;Sektoruebersetzung
TRANS1	SKEW	10,2,1			; 5" DD 512-BYTE / SEC
TRANS2	SKEW	15,4,1			; 8" DD 512-BYTE / SEC

;Angaben fuer Macro 

DPB0  	DPB	128,26, 77,1024,64,2	; 8" 77 TRK SS SD
DPB1  	DPB	512,15, 77,2048,128,2	; 8" 77 TRK SS DD
DPB2    DPB	512,15,154,2048,128,2	; 8" 77 TRK DS DD
--------------------------------^^^- Anzahl DIR Eintraege


aus dem macroeintrag wird:

AL0 = C0H = 2 Blöcke für das Dirctory
Zur besseren Lesbarkeit leicht modifiziert

                DPB1  	DPB	512,15,77,2048,128,2	; 8" 77 TRK SS DD
3C00      	DW	0021		; 128 BYTE RECORDS PER TRACK
040F      	DB	0022,0023	; BLOCK SHIFT AND MASK
00        	DB	0024		; EXTENT MASK
1801      	DW	0025		; MAXIMUM BLOCK NUMBER
7F00      	DW	0026		; MAXIMUM DIRECTORY ENTRY NUMBER
#C000      	DB	0027,0028	; ALLOC VECTOR FOR DIRECTORY
2000      	DW	0029		; CHECKSUM SIZE
0200      	DW	2		; OFFSET FOR SYSTEM TRACKS
0203      	DB	0030,0031	; PHYSICAL SECTOR SIZE SHIFT
                
                DPB2    DPB	512,15,154,2048,128,2	; 8" 77 TRK DS DD
3C00      	DW	0033		; 128 BYTE RECORDS PER TRACK
040F      	DB	0034,0035	; BLOCK SHIFT AND MASK
00        	DB	0036		; EXTENT MASK
3902      	DW	0037		; MAXIMUM BLOCK NUMBER
7F00      	DW	0038		; MAXIMUM DIRECTORY ENTRY NUMBER
#C000      	DB	0039,0040	; ALLOC VECTOR FOR DIRECTORY
2000      	DW	0041		; CHECKSUM SIZE
0200      	DW	2		; OFFSET FOR SYSTEM TRACKS
0203      	DB	0042,0043	; PHYSICAL SECTOR SIZE SHIFT




###########
 The disc statistics are stored in a parameter block (the DPB), 
 which contains the following information:

	DEFW	spt	;Number of 128-byte records per track
	DEFB	bsh	;Block shift. 3 => 1k, 4 => 2k, 5 => 4k....
	DEFB	blm	;Block mask. 7 => 1k, 0Fh => 2k, 1Fh => 4k...
	DEFB	exm	;Extent mask, see later
	DEFW	dsm	;(no. of blocks on the disc)-1
	DEFW	drm	;(no. of directory entries)-1
	DEFB	al0	;Directory allocation bitmap, first byte
	DEFB	al1	;Directory allocation bitmap, second byte
	DEFW	cks	;Checksum vector size, 0 for a fixed disc
			;No. directory entries/4, rounded up.
	DEFW	off	;Offset, number of reserved tracks

The directory allocation bitmap is interpreted as:

       al0              al1
b7b6b5b4b3b2b1b0 b7b6b5b4b3b2b1b0
 1 1 0 0 0 0 0 0  0 0 0 0 0 0 0 0        = C0H

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