DP Tool Club 8/CDASC08.ISO/NEWS/554/JUIN/EMSSTUFF.PAS

Pascal/Delphi Source File | 1993-10-07 | 3KB | 124 lines

{─ Fido Pascal Conference ────────────────────────────────────────────── PASCAL ─
Msg  : 533 of 614
From : Henrik Schmidt-Moeller              2:234/61.15          15 Jun 93  17:00
To   : Ian Lin                             1:249/140.0
Subj : Ems/Xms
────────────────────────────────────────────────────────────────────────────────
Hiya, Ian...

 > Hello (yet again). Who here knows how to access XMS or
 > EMS or both?

I've made some procedures for EMS addressing in TP. EMS uses a technic called
bank switching. It reserves a 64k area (EmmSeg) in memory for EMS and maps/
unmaps 16k EMS-pages in this area. Look at interrupt 67h for a complete list of
EMS commands. I haven't had time to comment on these procedures, so if you
don't understand them, feel free to ask. OK, here goes nothing...}

VAR
  EmmSeg,EmmHandle : Word;
  Err : Byte;

PROCEDURE DeallocateMem(Handle : Word); Forward;

PROCEDURE Error(E : String);
BEGIN
  DeallocateMem(Emmhandle);
  WriteLn(#7+E);
  Halt(1);
END;

PROCEDURE AllocateMem(LogPages : Word);
BEGIN
  ASM
  MOV  AH,43h
  MOV  BX,LogPages
  INT  67h
  MOV  Err,AH
  MOV  EmmHandle,DX
  END;
  CASE Err OF
    $80 : Error('AllocateMem: Internal error in EMS software');
    $81 : Error('AllocateMem: Malfunction in EMS software');
    $84 : Error('AllocateMem: Undefined function');
    $85 : Error('AllocateMem: No more handles available');
    $87 : Error('AllocateMem: Allocation requested more pages than
are'+#10+#13+ '             physically available; no pages allocated'); $88 :
Error('AllocateMem: Specified more logical pages than are'+#10+#13+ ' currently
available; no pages allocated'); $89 : Error('AllocateMem: Zero pages
requested'); END; END;

PROCEDURE MapEmm(PsyPage : Byte; LogPage : Word);
BEGIN
  ASM
  MOV  AH,44h
  MOV  AL,PsyPage
  MOV  BX,LogPage
  MOV  DX,EmmHandle
  INT  67h
  MOV  Err,AH;
  END;
  CASE Err OF
    $80 : Error('MapEmm: Internal error in EMS software');
    $81 : Error('MapEmm: Malfunction in EMS software');
    $83 : Error('MapEmm: Invalid handle');
    $84 : Error('MapEmm: Undefined function');
    $8A : Error('MapEmm: Logical page not assigned to this handle');
    $8B : Error('MapEmm: Physical page number invalid');
  END;
END;

PROCEDURE DeallocateMem(Handle : Word);
BEGIN
  ASM
  MOV  AH,45h
  MOV  DX,Handle
  INT  67h
  END;
END;

PROCEDURE GetPageSeg;
BEGIN
  ASM
  MOV  AH,41h
  INT  67h
  MOV  EmmSeg,BX
  MOV  Err,AH;
  END;
  CASE Err OF
    $80 : Error('GetPageSeg: Internal error in EMS software');
    $81 : Error('GetPageSeg: Malfunction in EMS software');
    $84 : Error('GetPageSeg: Undefined function');
  END;
END;

PROCEDURE GetMaxPages(VAR Num : Word);
VAR
  Dummy : Word;
BEGIN
  ASM
  MOV  AH,42h
  INT  67h
  MOV  Dummy,BX
  MOV  Err,AH;
  END;
  Num:=Dummy;
  CASE Err OF
    $80 : Error('GetMaxPages: Internal error in EMS software');
    $81 : Error('GetMaxPages: Malfunction in EMS software');
    $84 : Error('GetMaxPages: Undefined function');
  END;
END;

PROCEDURE WriteMem(Page : Byte;Pos : Integer;Ch : Char);
BEGIN
  Mem[EmmSeg:Page*$4000+Pos]:=Ord(Ch);
END;

PROCEDURE ReadMem(Page : Byte;Pos : Integer;VAR Ch : Char);
BEGIN
  Ch:=Chr(Mem[EmmSeg:Page*$4000+Pos]);
END;

I hope you find this useful.
Oh, by the way, REMEMBER to DEallocate!!!