/*
* 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 */