// DDTapes.d - Definitions for the Dual Density Tape I/O Routines
// Copyright Xerox Corporation 1981

// Last modified by Tim Diebert, March 16, 1981  4:18 PM

external
   [
// Procedures in the DDTapeIO package that are useful
   ActOnDDTape
   CloseDDTape
   EraseInches
   FileSkipFwd
   FileSkipRev
   OpenDDTape
   PerformVDDTCB
   RecSkipFwd
   RecSkipRev
   SetDensity
   TapeEOF
   TapeStatus
   TapeRewind
   TapeRewindWait
   TapeUnload
   WaitTapeReady

// Procedures in the DDTapeInit package that are useful
   InitializeDDTape

// Procedures in the DDTapeUtilA package that are useful
   DDTapeVertIntCode   // used by the R/W code for use to sync the Display turn off
   UBlockEq
   BlockEq
   UPupChecksum
   AsciiXlate
   EbcdicXlate
   TapeTfsSwatProc

// Procedures in the DDTape Microcode package that are useful
   DDTapeImage

// Statics or externals for use in other parts of the tape code
   DDTapeDispSaveData1
   DDTapeDispSaveData2
   DDTapeDispSaveData3
   DDTapeDispSavervDCBStart
   DDTapeVertIntFlag
   DDTapeVertIntMask
   DDTapeVertIntChannel
   TapeOpened
   TapeActive
   ]

manifest
   [
// Low core stuff and more
   DCBStart = #420 // Display start
   DCBInterupt = #421 // Display interupt field
   DDTCBStart = #622	// Tape Control Block Head
   IntVec = #501
   IntActive = #453
   MaxUnitNum = 3	// four drives: 0,1,2 and 3

// StartIO defs
   TapeNormalOp = #200
   TapeResetOp = #100
   ]

// Tape Controller Status Definitions
//--------------------------------------------------------------------------
structure DDStatus:
//--------------------------------------------------------------------------
   [
   RDY bit	//  100000 ReaDY. Unit loaded, Tape not in motion
   ONL bit	//   40000 ON Line. Unit loaded, Tape may be in motion
   RWD bit	//   20000 ReWinDing. Unit is rewinding
   FPT bit	//   10000 File ProTect. Write Ring removed.
   BOT bit	//    4000 Beginning Of Tape. Tape is at load point
   EOT bit	//    2000 End Of Tape. EOT marker was crossed in a forward direction
   FMK bit	//    1000 End Of File. Last record (R/W) was an EOF mark (Tape Mark)
   NRZI bit	//     400 NRZI Status is present in the drive. 800 bits per inch mode.
   HE bit	//     200 Hard Error.  A non recoverable error occured during R/W operation
   SE bit	//     100 Soft Error. A correctable error occured during R/W operation.
   DL bit	//      40 Data Late. Write or Read buffer went empty or overflowed
   RDP bit	//      20 Read Data Parity. A read parity error occured.
   ICL bit	//      10 InCorrect Length on write
   HDWERR bit	//       4 HarDWare ERRor. THe controller microcode detected an error.
   WFP bit	//       2 Write on File Protected reel. (FPT & Write-Op)
   CMDER bit	//       1 ComManD ERror. Unkown command type.
   ]

manifest
   [   // Status bit masks
   Bot = #4000
   Eot = #2000
   Eof = #1000
   Rewound = #144000	// RDY % ONL % BOT
   TapeErr = #367
   ]

// Tape Control Block as Required by the hardware
//--------------------------------------------------------------------------
structure DDTCB:
//--------------------------------------------------------------------------
   [
   ChainAddr   word	// Next TCB to be executed if error not detected by the current op.
   Command    word = 
      [
      Density bit 1	// 1 = NRZI mode, 0 = PE mode.
      Threshold bit 1	// 0 = normal, 1 = Low read threshold for data recovery.
      ReadAfterWrite bit 1	// 0 = no read data transfered after write, 1 = read trasnfered.
      blank bit 2	// should be zero
      Unit bit 3 	// Unit this op selects.
      blank bit 3	// should be zero
      Opcode bit 5 =	// Define both direction and action
         [
         REV bit 1	// Reverse direction bit
         WRT bit 1	// Write operation
         WFM bit 1	// File mark operation
         EDIT bit 1	// Edit spacing operation
         ERASE bit 1	// Erase or disable data
         ]
      ]
   ReadBuffer word	// Address of main memory read buffer
   ReadCount word	// Read buffer WORD count
   WriteBuffer word	// Address of main memory write buffer
   WriteCount word	// The number of BYTES to write.  May be odd
   ByteCount word	// Number of data bytes moved on R/W.
   Flags word =
      [
      @DDStatus       // Controller Ending Status
      ]
   ]
manifest
   [
// DDTCB size
   lDDTCB = ((size DDTCB)+15)/16

// Timeout timers for various things
   RewindTimeout = 19200   // The total time to rewind at 150ips
   RecordTimeout = 250   // Time to pass 25' of tape at 125ips
   FileTimeout = 23040   // Time to pass 2400' of tape at 125ips for a file search.
   NoOpTimeout = 10   // The total time to perform a NoOp
   ]
 

// Virtual Tape Control Block used by the software to keep track of things
//--------------------------------------------------------------------------
structure VDDTCB:   // virtual tape control block
//--------------------------------------------------------------------------
   [
   @DDTCB
   opDensity word	// flag indicating drives current density
   operation word	// Operation code as supplied to the software
   drive word	// Unit this operation is for
   errProc word	// Procedure to call in case an error is detected
   interventionProc word	// Procedure to call in case an operator intervention.
   retries word	// Retry count
   lowthresh word	// Flag used to keep track of a read at low threshold.
   timeout word	// Timeout flag. If true then timeout detected by PerformVTCB
   regap word	// Flag used to keep track of a long gap write during write retry
   ]

manifest
   [

// Operation Density Defs
   PE = 1600
   NRZI = 800

// VDDTCB size
   lVDDTCB = ((size VDDTCB)+15)/16

// Tape Op Codes as passed to the routines by the user program
// Assignments must be maintained so that the hardware gets what is needs.
   BackSpaceRecord = #21
   FwdSpaceRecord = #01
   BackSpaceFile = #25
   FwdSpaceFile = #05
   ReadFwd = #00
   ReadRev = #20
   ReadRevEdit = #22
   Write = #10
   WriteEdit = #12
   Erase = #15
   EraseVar = #11
   WriteEOF = #14
   Rewind = #35
   Unload = #36
   NoOp = #37
   Reset = #40
   ]

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