/*

* Copyright (c) 2006 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description: 

*

*	Frame Check Sequence checksums (FCS) for 16 and 32 bits.

*

*	The 16-bit version uses a 512-byte table (2 bytes * 256 elements)

*	and the 32-bit version uses a 1024-byte table (4 bytes * 256 elements)

*

*	Serial-based HDLC-like framing (RFC 1662) for use with the

*	CWDS serial protocol.

*	

*	Serial data is transmitted using an HDLC-like framing convention.

*	Byte-oriented streams are transmitted with a starting frame byte

*	and also followed by an ending frame byte and a checksum (FCS).

*	

*	Errors can be detected with high probability using the FCS.

*	While this is not intended to be used in an environment that

*	generates a large number of errors, nevertheless it can be

*	useful to help ensure that packets arrive with a high degree of

*	certainty and to allow data to be dropped and still allow

*	continuous data.

*	

*	Sender and receiver can be resynchronized with the receipt of a new

*	framing byte.

*	

*	

*	Frame Format

*	

*	The general frame format specified in RFC 1662 is described as:

*

*		+----------+----------+----------+

*		|   Flag   | Address  | Control  |

*		| 01111110 | 11111111 | 00000011 |

*		+----------+----------+----------+

*		+----------+-------------+---------+

*		| Protocol | Information | Padding |

*		| 8/16 bits|      *      |    *    |

*		+----------+-------------+---------+

*		+----------+----------+-----------------

*		|   FCS    |   Flag   | Inter-frame Fill

*		|16/32 bits| 01111110 | or next Address

*		+----------+----------+-----------------

*

*	The routines in this file use a subset and are not negotiated;

*	they are simply assumed. These are:

*	

*	Address and Control Field Compression is always ON.

*	Protocol Field Compression is always ON.

*	Protocol value is implied, but undefined.

*	Padding is OFF.

*	MRU is 1500 bytes.

*	FCS is 32 bits.

*	Trailing Flag is always transmitted.

*	

*	

*	The resulting frame format is:

*

*		+----------+

*		|   Flag   |

*		| 01111110 |

*		+----------+

*		+-------------+

*		| Information |

*		|      *      |

*		+-------------+

*		+----------+----------+-----------------

*		|   FCS    |   Flag   | Inter-frame Fill

*		|16/32 bits| 01111110 | or next Address

*		+----------+----------+-----------------

*	

*	Macros & Typedefs

*		

*		FCSBITSIZE

*		

*			This header file must first define FCSBITSIZE to be either one of:

*			FCS16 or FCS32.  These control the definitions for the rest of the header

*			file and the underlying tables.  Selecting FCS16 will cause the header

*			file to define 16-bit types, table, and functions for calculating the

*			16-bit FCS.  Selecting FCS32 is identical, except it uses 32-bit FCS values.

*			

*			FCS16 will use 512 bytes (2 bytes * 256 entries) of constant data space.

*			FCS32 will use 1024 bytes.

*	

*		FCSType

*		

*			The 16- or 32-bit type used for the FCS register and datum.

*

*		PPPINITFCS

*			

*			Initialize the FCS register with this value.

*		

*		PPPGOODFCS

*		

*			On the receiver side, after the FCS compute function is applied

*			to all data bytes plus the two or four FCS bytes, the correct FCS

*			value will be PPPGOODFCS, a constant.

*		

*		PPPCOMPFCS

*

*

*	REFERENCES

*

*	[RFC1662.94]	Simpson, W., Editor, "PPP in HDLC-like Framing,"

*					STD 51, RFC 1662, Daydreamer, July 1994.

*

*/

#ifndef TRK_SERFRAME_H

#define TRK_SERFRAME_H

#define FCS8  0					/* SCM: Added for simple 8-bit checksums */

#define FCS16 1

#define FCS32 2

#define	FCSBITSIZE FCS8			/* define as either FCS8, FCS16 or FCS32 */

#if FCSBITSIZE == FCS8

	/*

	 *	Definitions for 8-bit simple Frame Check Sequences

	 */

	typedef unsigned char FCSType;	/* 8-bit type */

	#define PPPINITFCS8		0x00		/* Initial FCS value */

	#define PPPGOODFCS8		0xFF		/* Good final FCS value */

	#define PPPINITFCS		PPPINITFCS8

	#define PPPGOODFCS		PPPGOODFCS8

	#define PPPCOMPFCS		0xFF		/* complement FCS value */

	#ifdef __cplusplus	

		inline FCSType PPPFCS(FCSType fcs, unsigned char c)

		{

			return (fcs + c);

		}

	#else

		#define PPPFCS(fcs, c)	(fcs + c)

	#endif

#elif FCSBITSIZE == FCS16

	/*

	 *	Definitions for 16-bit Frame Check Sequences

	 */

	typedef unsigned short FCSType;	/* 16-bit type */

/*	extern FCSType fcstab[]; */

	extern const FCSType fcstab[256];

	#define PPPINITFCS16	0xffff		/* Initial FCS value */

	#define PPPGOODFCS16	0xf0b8		/* Good final FCS value */

	#define PPPINITFCS		PPPINITFCS16

	#define PPPGOODFCS		PPPGOODFCS16

	#define PPPCOMPFCS		0xffff		/* complement FCS value */

	#if __cplusplus	

		inline FCSType PPPFCS(FCSType fcs, unsigned char c)

		{

			return (((fcs) >> 8) ^ fcstab[((fcs) ^ (c)) & 0xff]);

		}

	#else

		#define PPPFCS(fcs, c)	(((fcs) >> 8) ^ fcstab[((fcs) ^ (c)) & 0xff])

	#endif

#elif FCSBITSIZE == FCS32

	/*

	 *	Definitions for 32-bit Frame Check Sequences

	 */

	typedef unsigned long FCSType;	/* 32-bit FCS */

/*	extern FCSType fcstab_32[]; */

	extern const FCSType fcstab_32[256];

	#define PPPINITFCS32 	0xffffffff	/* Initial FCS value */

	#define PPPGOODFCS32 	0xdebb20e3	/* Good final FCS value */

	#define PPPINITFCS		PPPINITFCS32

	#define PPPGOODFCS		PPPGOODFCS32

	#define PPPCOMPFCS		0xffffffff	/* complement FCS value */

	#if __cplusplus

		inline FCSType PPPFCS(FCSType fcs, unsigned char c)

		{

			return (((fcs) >> 8) ^ fcstab_32[((fcs) ^ (c)) & 0xff]);

		}

	#else

		#define PPPFCS(fcs, c) (((fcs) >> 8) ^ fcstab_32[((fcs) ^ (c)) & 0xff])

	#endif

#endif

/****************************************************************************/

/*

 *	Constants used for framing serial data

 */

/****************************************************************************/

#define	PPP_UI			0x03	/* Unnumbered Information */

#define	PPP_FLAG		0x7e	/* Flag Sequence */

#define	PPP_ESCAPE		0x7d	/* Asynchronous Control Escape */

#define	PPP_TRANS		0x20	/* Asynchronous transparency modifier */

#define MAXFRAMESIZE	0x1000	/* maximum unframed/unescaped data size */

#endif /* ndef TRK_SERFRAME_H */