DEFINITION MODULE MiscPMOS;

        (************************************************)
        (*                                              *)
        (*      Miscellaneous PMOS procedures           *)
        (*                                              *)
        (*  Programmer:         P. Moylan               *)
        (*  Last edited:        8 May 1997              *)
        (*  Status:             OK                      *)
        (*                                              *)
        (************************************************)

IMPORT SYSTEM;

TYPE RegisterPacket =
                (* We don't bother covering everything here, just       *)
                (* the registers we have a need for.                    *)
                RECORD
                    CASE :BOOLEAN OF
                     | FALSE:   AL, AH, BL, BH, CL, CH, DL, DH: SYSTEM.BYTE;
                     | TRUE:    AX, BX, CX, DX, BP, SI, DI, DS, ES: CARDINAL;
                    END (*CASE*);
                END (*RECORD*);

     CMOSaddress = CARDINAL[0..63];

(************************************************************************)
(*                              STRING COPY                             *)
(************************************************************************)

PROCEDURE CopyString (source: ARRAY OF CHAR;  VAR (*OUT*) dest: ARRAY OF CHAR);

    (* Copies a string, with truncation or null termination as needed.  *)
    (* This function is provided in order to help software portability, *)
    (* i.e. to avoid having to rewrite code for no reason other than    *)
    (* a change of compilers.                                           *)

(************************************************************************)
(*                          STRING COMPARISON                           *)
(************************************************************************)

PROCEDURE Compare (first, second: ARRAY OF SYSTEM.LOC): INTEGER;

    (* Returns >0 if first>second, 0 if first=second, <0 if             *)
    (* first<second.  The comparison is bytewise, from the left,        *)
    (* treating each byte as an unsigned number.                        *)

(************************************************************************)
(*                   MISCELLANEOUS LOW-LEVEL OPERATIONS                 *)
(************************************************************************)

PROCEDURE EnterCriticalSection(): CARDINAL;

    (* Saves the processor flags word, including the current "interrupt *)
    (* enable" status, on the caller's stack, and returns with          *)
    (* interrupts disabled.   NOTE: this procedure and the following    *)
    (* one should be used as a matched pair.                            *)

PROCEDURE LeaveCriticalSection (savedPSW: CARDINAL);

    (* Restores the processor flags word, including the "interrupt      *)
    (* enable" status, from the stack.  NOTE: this procedure and the    *)
    (* one above should be used as a matched pair.                      *)

(************************************************************************)
(*       The remaining procedures in this module are unavailable,       *)
(*             because of incompatibility with OS/2                     *)
(************************************************************************)

(*
(************************************************************************)
(*                      PROCEDURES TO ACCESS CMOS                       *)
(************************************************************************)
(*                                                                      *)
(*  The first 14 bytes of CMOS are used for the real-time clock - see   *)
(*  module TimeOfDay for details.                                       *)
(*                                                                      *)
(*  The contents of the remaining bytes would take too long to describe *)
(*  here, so only the ones of current interest are mentioned:           *)
(*                                                                      *)
(*      10H     Diskette drive type.  The high order 4 bits describe    *)
(*              drive A, the lower order 4 bits describe drive B.       *)
(*              The encoding is:                                        *)
(*                      0       no drive present                        *)
(*                      1       double sided drive, 48 TPI              *)
(*                      2       high capacity drive, 96 TPI             *)
(*                      4       3.5" 1.44MB drive                       *)
(*                  (other values are reserved).                        *)
(*                                                                      *)
(************************************************************************)

PROCEDURE ReadCMOS (location: CMOSaddress): SYSTEM.BYTE;

    (* Returns the value at the given CMOS location.    *)

PROCEDURE WriteCMOS (location: CMOSaddress;  value: SYSTEM.BYTE);

    (* Stores a value at the given CMOS location.       *)

(************************************************************************)
(*                         BIOS/MS-DOS CALLS                            *)
(************************************************************************)

PROCEDURE BIOS (InterruptNumber: CARDINAL;
                        VAR (*INOUT*) Registers: RegisterPacket);

    (* Performs a software interrupt, with the given interrupt number,  *)
    (* after loading the components of variable "Registers" into the    *)
    (* machine registers.  After the handler returns, the updated       *)
    (* register values are put back into variable "Registers".          *)

PROCEDURE ProcessorStatus(): CARDINAL;

    (* Returns the current value of the processor flags word.   *)

PROCEDURE ShortDelay (amount: CARDINAL);

    (* Provides a time delay for those cases where the required delay   *)
    (* is not long enough to justify a Sleep() operation.               *)
    (* The present version is not entirely satisfactory - needs to be   *)
    (* re-tuned for different compiler options, different processor     *)
    (* models, etc.  This should be seen as an interim solution only.   *)
*)

END MiscPMOS.
