/*
 * Copyright (c) 2002,2016 Mario de Sousa (msousa@fe.up.pt)
 *
 * This file is part of the Modbus library for Beremiz and matiec.
 *
 * This Modbus library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser 
 * General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this Modbus library.  If not, see <http://www.gnu.org/licenses/>.
 *
 * This code is made available on the understanding that it will not be
 * used in safety-critical situations without a full and competent review.
 */



#ifndef MB_UTIL_H
#define MB_UTIL_H

/* This file has constants related to the modbus protocol */
/*
 * Some of these constants are specific to the layer two protocols
 * (i.e. master and slave), while others are specific of the
 * layer one protocols (i.e. rtu, ascii, tcp).
 *
 * a) Unfortunately, due to the nature of the modbus protocol, that does not
 * include a frame size field in the layer 1 frame (see note 1), and the
 * fact that we are implementing it at the user level, the implementation
 * of some layer 1 protocols need to know the content of the layer 2 protocol
 * in order to determine the size of the frame.
 *
 * b) The layer two message formats are in fact the same, just reversing the role
 * being played (master or slave).
 *
 * Bothe a) and b) mean we need the same modbus protocol constants in several files.
 * It ends up making more sense to put them all together in a single file, which
 * makes updating easier, even though we are trying to strictly seperate the layer 1
 * and layer 2 protocols.
 *
 *
 *
 * Notes:
 *  (1) There is no layer 1 field with the frame size, nevertheless this
 *      size can be determined indirectly due to timing restrictions on the rtu
 *      protocol. Unfortunately, due to the fact that we are implementing
 *      it at the user level, we are not guaranteed to detect these timings
 *      correctly, and therefore have to rely on layer 2 protocol info to
 *      determine the frame size.
 *      For the ascii protocol, the frame size is determined indirectly by
 *      a frame header and tail, so we do not use layer 2 protocol info.
 */


 /* Layer 2 Frame Structure...                */
 /* Valid for both master and slave protocols */
#define L2_FRAME_HEADER_LENGTH    6
#define L2_FRAME_BYTECOUNT_LENGTH 1
#define L2_FRAME_DATABYTES_LENGTH 255
#define MAX_L2_FRAME_LENGTH (L2_FRAME_HEADER_LENGTH + L2_FRAME_BYTECOUNT_LENGTH +    \
                             L2_FRAME_DATABYTES_LENGTH)

#define L2_FRAME_SLAVEID_OFS    0
#define L2_FRAME_FUNCTION_OFS   1

 /* Layer 1 - Ascii Frame sizes... */
#define L2_TO_ASC_CODING        2 /* number of ascii bytes used to code a Layer 2 frame byte */
#define ASC_FRAME_HEADER_LENGTH 1
#define ASC_FRAME_HEADER        ':'
#define ASC_FRAME_TAIL_LENGTH   2
#define ASC_FRAME_TAIL_0        '\13' /* 'CR' */
#define ASC_FRAME_TAIL_1        '\10' /* 'LF' */
#define ASC_FRAME_LRC_LENGTH    2

 /* Layer 1 - RTU Frame sizes... */
#define RTU_FRAME_CRC_LENGTH    2

 /* Layer 1 - TCP Frame sizes... */
#define TCP_HEADER_LENGTH       6

 /* Global Frame sizes */
#define MAX_RTU_FRAME_LENGTH (MAX_L2_FRAME_LENGTH + RTU_FRAME_CRC_LENGTH)
#define MAX_ASC_FRAME_LENGTH ((MAX_L2_FRAME_LENGTH * L2_TO_ASC_CODING) +             \
                              ASC_FRAME_HEADER_LENGTH + ASC_FRAME_TAIL_LENGTH +      \
                              ASC_FRAME_LRC_LENGTH)
                              

/* Modbus Exception codes */
#define ERR_ILLEGAL_FUNCTION                        0x01
#define ERR_ILLEGAL_DATA_ADDRESS                    0x02 
#define ERR_ILLEGAL_DATA_VALUE                      0x03 
#define ERR_SLAVE_DEVICE_FAILURE                    0x04 
#define ERR_ACKNOWLEDGE                             0x05 
#define ERR_SLAVE_DEVICE_BUSY                       0x06 
#define ERR_NEGATIVE_ACKNOWLEDGE                    0x07 
#define ERR_MEMORY_PARITY_ERROR                     0x08 
#define ERR_GATEWAY_PATH_UNAVAILABLE                0x0A 
#define ERR_GATEWAY_TARGET_DEVICE_FAILED_TO_RESPOND 0x0B 



#endif  /* MB_UTIL_H */