The Programmer's Guide to TRSDOS Version 6 - Tim Mann's Home ...

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4.3 DISK CONTROLLER COMMUNICATIONS The function of DISK CONTROLLER COMMUNICATIONS is to communicate operating system commands to a disk driver so that the driver can translate these commands into commands acceptable to the disk controller. Before we look at the command functions provided by the system, let's take a look at the commands available in a typical floppy disk controller - the Western Digital 179X series. Figure 4-2 summarizes these commands. If you are interested in the detailed specifications of such a controller, you should obtain the "FD 179X-02 Floppy Disk Formatter/Controller Family" manual published by the Western Digital Corporation. Command Purpose RESTORE Recalibrate drive to cylinder 0 position SEEK Reposition head to a specified cylinder STEP Move the head one cylinder position STEP IN Move the head one cylinder to the higher track STEP OUT Move the head one cylinder to the lower track READ SECTOR Transfer the specified sector from disk to CPU WRITE SECTOR Transfer the specified sector from CPU to disk READ ADDRESS Transfer data from the next ID FIELD encountered READ TRACK Transfer an entire track of data from disk to CPU WRITE TRACK Transfer an entire track of data from CPU to disk FORCE INTERRUPT Abort the pending controller operation Figure 4-2: Floppy Disk Controller Commands Since the DOS also supports hard disk drives, let's look at the commands available in some typical hard disk controllers. The following three figures will summarize the commands supported by the Lobo Drives UniVersal (UVC), the Western Digital WD-1000, and the XEBEC S-1410 controllers. Command Purpose NO OPERATION Test if controller available READ SECTOR Transfer the specified sector from disk to CPU READ DISK Read entire disk without data transfer WRITE SECTOR Transfer the specified sector from CPU to disk FORMAT DISK Format entire disk READ UNTIL FLAW Read disk until encountering an error Figure 4-3: Lobo-UVC Controller Commands If we compare the typical Hard Disk Controller [let's abbreviate this term to "HDC"] commands to the commands available in the typical Floppy Disk Controller [we will also abbreviate this term to "FDC"], we find that the HDC generally has very few commands for communication between the CPU [most hard disk systems refer to the CPU as the "HOST"] and the controller. The S-1410 HDC has a preponderance of commands; however, close examination reveals many commands for testing and diagnostics. Each HDC mentioned performs its own automatic SEEK operation; therefore, it is generally not even necessary for the HDC driver to utilize that command. The HDC driver will most typically involve READ, WRITE, and FORMAT operations. 4-9
Command Purpose RESTORE Recalibrate drive to track 0 SEEK Position the read/write head to a cylinder READ SECTOR Transfer the specified sector from disk to CPU WRITE SECTOR Transfer the specified sector from CPU to disk FORMAT TRACK Initialize the ID and DATA fields of the track Figure 4-4: WD-1000 Controller Commands Command Purpose TEST DRIVE READY Test if drive is ready RECALIBRATE Recalibrate drive to track 0 REQUEST SENSE STATUS Return the 4-byte drive/controller status FORMAT DRIVE Format entire disk CHECK TRACK FORMAT Check track for correct ID and interleave FORMAT TRACK Initialize the ID and DATA fields of the track READ Read the specified sector(s) from disk to CPU WRITE Write the specified sector(s) from CPU to disk SEEK Position the read/write head to a cylinder INITIALIZE DRIVE CHARACTERISTICS Configure controller for drive READ ECC BURST ERROR LENGTH Read the byte containing ECC data RAM DIAGNOSTIC Test the controller's RAM buffer DRIVE DIAGNOSTIC Test the drive-to-controller interface CONTROLLER INTERNAL Perform controller self-test DIAGNOSTICS READ LONG Read a sector and four ECC bytes WRITE LONG Write a sector and four ECC bytes Figure 4-5: S-1410 Controller Commands The process of drive selection is unique from HDC to HDC as well as the adapter that electronically interfaces the HDC to the host. FDC drivers are typically more involved with the additional commands for stepping and seeking while performing a little more bookkeeping operations. There is also a great more involvement in the format operation for the FDC driver over the HDC driver. The DOS provides 16 SuperVisor Calls that are used to pass operating system function requests to a disk controller - be it an FDC or an HDC. Figure 4-6 reviews these functions that are detailed in chapter 7. If we try to correlate the SVC functions with the FDC commands, we observe that the DOS provides no facility for requesting a STEP, STEP OUT, nor a FORCE INTERRUPT. This is not an oversight. The force interrupt is a function that is not needed from a higher level such as the DOS, but would most likely be usable directly within the FDC driver. Also, since the FDC does its own track stepping via the SEEK request, the STEP command from the DOS is only needed during the format operation. The DOS limits this to STEP IN since the disk only needs to be stepped in one direction during the format operation. The remaining SVCs supply the higher level functions to communicate all of the DOS requests to the controller. 4-10
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 and 34: accessed a single-sided diskette, t
Page 35: containing the disk's directory. Th
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
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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.
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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
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===================================
Page 127 and 128:
The TYPE=0A indicates that it is th
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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
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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
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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
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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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