DEFINITION MODULE MiscPMOS;

	(************************************************)
	(*						*)
	(*	Miscellaneous PMOS procedures		*)
	(*						*)
	(*  Programmer:		P. Moylan		*)
	(*  Last edited:	24 August 1994		*)
	(*  Status:		OK			*)
	(*						*)
	(************************************************)

IMPORT SYSTEM;

TYPE RegisterPacket =
		(*<TopSpeed*) SYSTEM.Registers; (*>*)
		(*<FST
		(* 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 = [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.						*)

(************************************************************************)
(*			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".		*)

(************************************************************************)
(*		     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.			*)

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.