MODULE PrivateTimer;

(**
	Author: Alexey Morozov, HighDim GmbH, 2013
	Purpose: implementation of the driver for ARM Cortex-A9 MPCore private timer
*)

IMPORT
	SYSTEM;

CONST
	(* register offsets *)
	LoadOffset = 00H;
	CounterRegOffset = 04H;
	ControlRegOffset = 08H;
	IsrRegOffset = 00CH;

	(* control register masks *)
	ControlEnableMask = {0};
	ControlAutoReloadMask = {1};
	ControlIrqEnableMask = {2};
	ControlPrescalerMask = SYSTEM.VAL(SET,00000FF00H);

TYPE
	
	(**
		Timer descriptor
	*)
	Timer* = RECORD
		baseAddr-: ADDRESS; (** timer base address *)
	END;

	(**
		Initialize a timer given a private timer bas address
	*)
	PROCEDURE Init*(VAR timer: Timer; baseAddress: ADDRESS);
	BEGIN		
		timer.baseAddr := baseAddress;
	END Init;

	(**
		Get private timer counter value

		Remarks:
			counter value changes decrementally from the initial value set by LoadTimer

	*)
	PROCEDURE GetCounterValue*(CONST timer: Timer): LONGINT;
	BEGIN
		RETURN SYSTEM.GET32(timer.baseAddr+CounterRegOffset);
	END GetCounterValue;

	(**
		Load timer with a given 32-bit initial counter value
	*)
	PROCEDURE LoadTimer*(VAR timer: Timer; value: LONGINT);
	BEGIN
		SYSTEM.PUT32(timer.baseAddr+LoadOffset,value);
	END LoadTimer;

	(** Start timer *)
	PROCEDURE Start*(VAR timer: Timer);
	BEGIN
		SYSTEM.PUT32(timer.baseAddr+ControlRegOffset,SYSTEM.VAL(SET,SYSTEM.GET32(timer.baseAddr+ControlRegOffset))+ControlEnableMask);
	END Start;

	(** Stop timer *)
	PROCEDURE Stop*(VAR timer: Timer);
	BEGIN
		SYSTEM.PUT32(timer.baseAddr+ControlRegOffset,SYSTEM.VAL(SET,SYSTEM.GET32(timer.baseAddr+ControlRegOffset))-ControlEnableMask);
	END Stop;

	(** Enable/Disable auto reload of the timer counter *)
	PROCEDURE EnableAutoReload*(VAR timer: Timer; enable: BOOLEAN);
	BEGIN
		IF enable THEN
			SYSTEM.PUT32(timer.baseAddr+ControlRegOffset,SYSTEM.VAL(SET,SYSTEM.GET32(timer.baseAddr+ControlRegOffset))+ControlAutoReloadMask);
		ELSE
			SYSTEM.PUT32(timer.baseAddr+ControlRegOffset,SYSTEM.VAL(SET,SYSTEM.GET32(timer.baseAddr+ControlRegOffset))-ControlAutoReloadMask);
		END;
	END EnableAutoReload;

	(**
		Set 8-bit timer clock prescaler value
	*)
	PROCEDURE SetPrescaler*(VAR timer: Timer; value: LONGINT);
	VAR reg: LONGINT;
	BEGIN
		reg := SYSTEM.GET32(timer.baseAddr+ControlRegOffset);
		(* clear all prescaler control bits and set the prescaler value *)
		SYSTEM.PUT32(timer.baseAddr+ControlRegOffset,SYSTEM.VAL(SET,reg)-ControlPrescalerMask+SYSTEM.VAL(SET,LSH(value,8)));
	END SetPrescaler;

	(**
		Get 8-bit timer clock prescaler value
	*)
	PROCEDURE GetPrescaler*(CONST timer: Timer): LONGINT;
	BEGIN
		RETURN LSH(SYSTEM.VAL(LONGINT,SYSTEM.VAL(SET,SYSTEM.GET32(timer.baseAddr+ControlRegOffset)) * ControlPrescalerMask),-8);
	END GetPrescaler;

	(** Enable/disable timer interrupt *)
	PROCEDURE EnableInterrupt*(VAR timer: Timer; enable: BOOLEAN);
	BEGIN
		IF enable THEN
			SYSTEM.PUT32(timer.baseAddr+ControlRegOffset,SYSTEM.VAL(SET,SYSTEM.GET32(timer.baseAddr+ControlRegOffset))+ControlIrqEnableMask);
		ELSE
			SYSTEM.PUT32(timer.baseAddr+ControlRegOffset,SYSTEM.VAL(SET,SYSTEM.GET32(timer.baseAddr+ControlRegOffset))-ControlIrqEnableMask);
		END;
	END EnableInterrupt;

	(** Get timer interrupt status

		Remark:
			returned status value indicates the timer counter register has reached zero
	*)
	PROCEDURE GetInterruptStatus*(CONST timer: Timer): LONGINT;
	BEGIN
		RETURN SYSTEM.GET32(timer.baseAddr+IsrRegOffset);
	END GetInterruptStatus;

	(**
		Clear timer interrupt status
	*)
	PROCEDURE ClearInterruptStatus*(VAR timer: Timer);
	BEGIN
		SYSTEM.PUT32(timer.baseAddr+IsrRegOffset,SYSTEM.VAL(SET,SYSTEM.GET32(timer.baseAddr+IsrRegOffset)) - {0});
	END ClearInterruptStatus;

END PrivateTimer.