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cylinders were a single cylinder with twice as much capacity (although the system will still limit the logical cylinder to not exceed 256 sectors). In that case, the MAXCYL entry will be half of the actual quantity and bit-5 of the FLAG-2 field will be set. For example, an SA-1000 drive (8" winchester) has 256 cylinders, four surfaces, and 32 sectors per track. If this drive is treated as a single volume (no partitioning), the MAXCYL entry is X'7F' indicating the highest numbered cylinder is 127 (128 cylinders). The DBLBIT bit is set indicating a logical cylinder is composed of two physical cylinders. 4.2.6 CONFIGURATION FIELD - This two-byte field contains information concerning the physical space parameters of the disk drive and how space is allocated per cylinder. Its entries are encoded as follows: 4.2.6.1 Byte 7 Bits 7-5 This subfield contains the number of heads (surfaces) assigned to the logical partition of a hard disk drive. In the case of floppy disk drives, this entry should be a B'000'. For example, a four-head hard drive with a two-head partition would have a B'001' in this subfield. The entry is zero relative, thus a one-head partition is B'000', a two-head partition would be B'001', and an eight-head partition would be B'111'. Bits 4-0 This subfield contains the highest numbered sector on a track numbered relative from zero. A ten-sector-per-track drive would show an X'09' entry. A 32-sector-per-track hard drive would show an X'1F'. 4.2.6.2 Byte 8 Bits 7-5 This subfield contains the quantity of granules per track allocated to the disk drive according to the number of sectors per granule. Since the field is 3-bits in length, the entry is offset from zero. Thus, one granule per track is entered as B'000', two as B'001', etc. In the case of floppy disk drives, this figure is standardized for 5-1/4" and 8" media as identified in chapter 5. If the DCT is associated with a hard drive, then the figure entered here refers to the number of granules in a physical cylinder according to the number of surfaces. If the DBLBIT bit is set, this entry then represents half of the granules on a logical cylinder. The total granules per logical cylinder is computed by the doubling the value contained in this field if bit-5 of DCT FLAG-2 is set. Let's illustrate this again using the SA-1000 drive. If we configure the drive as a single volume with 16 sectors per granule, a physical track has two granules per track. Since the drive has four surfaces, a physical cylinder has eight granules. However, since the DBLBIT bit must be set to indicate double the 128 cylinders shown in the MAXCYL field, the system would have to double the granules per cylinder computing 16 GPC. This is clearly in violation of the system's upper limit of eight granules per cylinder maximum. Therefore, our example SA-1000 drive would be configured with 32 sectors per granule, one granule per track, four granules per physical cylinder. The DBLBIT bit would provide eight logical granules per logical cylinder. Therefore, this subfield would have an entry to indicate four granules. Bits 4-0 This field contains the quantity of sectors per granule that is used in the configuration of the disk. In the case of floppy disk drives, this figure is standardized for 5-1/4" and 8" media as identified in chapter 5. Hard disk drive granule sizes are assigned by the implementor of the hard disk drive system. 4.2.7 DIRCYL - This field contains the cylinder where the directory is located. For any directory access, the system will use the contents of this field as a pointer to the cylinder 4-7
containing the disk's directory. The system attempts to maintain the integrity of this field by using the status returned when the driver reads a system sector in contrast to a non-system sector (chapter 5 discusses the use of data address mark conventions in disk sectors). If the system expects to be reading a directory sector but does not get the error code 6 ("Attempted to read system data sector"), it will read the BOOT sector and obtain the directory cylinder storage byte located therein for a second attempt to read the directory sector. After an unsuccessful second attempt (including whatever retries are performed per attempt by the driver), the system posts a read or write error depending on the original request. This error will eventually be classified as a GAT , HIT or DIRECTORY error if the attempt was an I/O request for the GAT, HIT or a directory entry sector respectively. Realizing that most hard disk controllers do NOT support a data address mark convention, the hard disk driver must simulate the READ SYSTEM SECTOR error code when an @RDSEC or @VRSEC request is made to the directory cylinder. Since the only indication of where the directory is located is contained in this field, it is paramount to the functioning of the hard disk environment that this field be correctly maintained. The system's LOG command will always reload this field with the BOOT sector's directory cylinder pointer. Thus, it may be necessary to highlight the function of LOG in any written information pertinent to the hard disk system user. ____________________________________________________________________ | | | | | | | | | | | | | VECTOR | FLAG | FLAG | CUR | MAX |H M S| G S | DIR | |C3/C9| ADDRESS | 1 | 2 | CYL | CYL |D A E| P P | CYL | |_____|______|______|______|______|______|______|S__X_C|_T__G_|______| Figure 4-1: Drive Control Table Record 4-8
Page 1 and 2: MISOSYS, INC. The Programmer's Guid
Page 3 and 4: 1. Introduction Many thousands of u
Page 5 and 6: language (i.e. BASIC, C, PASCAL, ..
Page 7 and 8: NAME START END DESCRIPTION LOWCORE
Page 9 and 10: ackup utility provides exceptional
Page 11 and 12: 3. Device Input/Output Interfacing
Page 13 and 14: 3.2.2 VECTOR Field - This field in
Page 15 and 16: FILTER *PR USING *S0 the operating
Page 17 and 18: ===================================
Page 19 and 20: ===================================
Page 21 and 22: ENTRY JR BEGIN ;Branch around linka
Page 23 and 24: DATA1 EQU $-DATA$ DB 0 ;Data storag
Page 25 and 26: Offset Contents +0 Contains the las
Page 27 and 28: image of the serial port UART statu
Page 29 and 30: called TRACKs. Each track is then d
Page 31 and 32: The DCT contains the information re
Page 33: accessed a single-sided diskette, t
Page 37 and 38: Command Purpose RESTORE Recalibrate
Page 39 and 40: available from Logical Systems, Inc
Page 41 and 42: exceeds this capacity, then it must
Page 43 and 44: is two physical cylinders. Although
Page 45 and 46: 5. The DOS Directory Structure 5.1
Page 47 and 48: ===================================
Page 49 and 50: 5.2.8 PACK NAME - This field conta
Page 51 and 52: The position of a file's hash code
Page 53 and 54: 5.4 THE DIRECTORY RECORD STRUCTURE
Page 55 and 56: Bit 3 Specifies the visibility; if
Page 57 and 58: the first granule in use is the sec
Page 59 and 60: travels the turnpike. In this manne
Page 61 and 62: The @FSPEC SVC will transfer the fi
Page 63 and 64: A high level language permits you t
Page 65 and 66: does exist, @RENAME should return e
Page 67 and 68: Next, it would be very useful if th
Page 69 and 70: LD HL,FCBX+9 ;Point to the LRL fiel
Page 71 and 72: operating system for such a purpose
Page 73 and 74: position where the last character i
Page 75 and 76: ecord. If a file has more than four
Page 77 and 78: DE Contains a pointer to the File C
Page 79 and 80: @RENAM SVC-56 Rename a file on disk
Page 81 and 82: @FNAME SVC-80 Obtain filespec given
Page 83 and 84: @WRSEC SVC-53 Write a disk sector @
Page 85 and 86:
7.6 SUPERVISOR CALL DETAILS 7.6.1 @
Page 87 and 88:
Note: @EXIT in SYS1 automatically r
Page 89 and 90:
7.6.10 @CLOSE SVC-60 This SVC will
Page 91 and 92:
7.6.18 @DCSTAT SVC-40 This SVC pass
Page 93 and 94:
Directory to Buffer Entry: B 1; Fun
Page 95 and 96:
7.6.31 @FLAGS$ SVC-101 This SVC wil
Page 97 and 98:
NFLAG$ This "network" flag is used
Page 99 and 100:
7.6.32 @FNAME SVC-80 This SVC will
Page 101 and 102:
7.6.40 @HEX8 SVC-98 This SVC will c
Page 103 and 104:
7.6.48 @KLTSK SVC-32 This SVC will
Page 105 and 106:
7.6.57 @OPEN SVC-59 This SVC will o
Page 107 and 108:
Registers Affected: AF, BC. Entry:
Page 109 and 110:
0-14 FILENAME/EXT:D - left justifie
Page 111 and 112:
7.6.71 @REMOV SVC-57 This SVC will
Page 113 and 114:
Entry: DE A pointer to the FCB cont
Page 115 and 116:
Exit: A Error return code, if any.
Page 117 and 118:
CURSOR CHARACTER Registers Affected
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Exit: A Will contain the error code
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esident routine into its execution
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CKPAWS LD A,@FLAGS$ ;Get Flags poin
Page 125 and 126:
===================================
Page 127 and 128:
The TYPE=0A indicates that it is th
Page 129 and 130:
Error 08: Device not available A re
Page 131 and 132:
Error 28: End of file encountered T
Page 133 and 134:
8.5 HEADER PROTOCOL OF MEMORY MODUL
Page 135 and 136:
This is obviously an extremely usel
Page 137 and 138:
LD (IX+2),15 JR TASKA By firmly und
Page 139 and 140:
8.7.3 Details of Low Memory Page 2
Page 141 and 142:
actual bank switching. As previousl
Page 143 and 144:
set. Thus, the Z-flag will be indic
Page 145 and 146:
8.10 SYSTEM DISK BOOT TRACK The ope
Page 147 and 148:
14 DEBUG 72 PURGE 1B VERIFY 71 DUMP
Page 149 and 150:
8.13 USING @PARAM The @PARAM SuperV
Page 151 and 152:
DW LPARM+1 DB 'FEED ' ;Line feed pa
Page 153 and 154:
;*=*=* PPARM LD BC,0 ;Zero because
Page 155 and 156:
8.14 TRAP Filter Illustrated ;TRAP/
Page 157 and 158:
8.15 SLASH0 Filter Illustrated ;SLA
Page 159 and 160:
8.16 DMP-500 BOLDFACE Filter Illust
Page 161 and 162:
NOMEM$ DB 'High memory is not avail
Page 163 and 164:
@ @ABORT..........7-2, 7-4, 7-8, 7-
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