1 //---------------------------------------------------------------------------
2 // Copyright (C) 2000 Dallas Semiconductor Corporation, All Rights Reserved.
4 // Permission is hereby granted, free of charge, to any person obtaining a
5 // copy of this software and associated documentation files (the "Software"),
6 // to deal in the Software without restriction, including without limitation
7 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 // and/or sell copies of the Software, and to permit persons to whom the
9 // Software is furnished to do so, subject to the following conditions:
11 // The above copyright notice and this permission notice shall be included
12 // in all copies or substantial portions of the Software.
14 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
15 // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
16 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
17 // IN NO EVENT SHALL DALLAS SEMICONDUCTOR BE LIABLE FOR ANY CLAIM, DAMAGES
18 // OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
19 // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
20 // OTHER DEALINGS IN THE SOFTWARE.
22 // Except as contained in this notice, the name of Dallas Semiconductor
23 // shall not be used except as stated in the Dallas Semiconductor
25 //--------------------------------------------------------------------------
27 // crcutil.c - Keeps track of the CRC for 16 and 8 bit operations
30 // tinihack, data is a reserved keyword for sdcc. So:
36 // Local global variables
37 static ushort utilcrc16[MAX_PORTNUM];
38 static uchar utilcrc8[MAX_PORTNUM];
39 static short oddparity[16] = { 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };
40 static uchar dscrc_table[] = {
41 0, 94,188,226, 97, 63,221,131,194,156,126, 32,163,253, 31, 65,
42 157,195, 33,127,252,162, 64, 30, 95, 1,227,189, 62, 96,130,220,
43 35,125,159,193, 66, 28,254,160,225,191, 93, 3,128,222, 60, 98,
44 190,224, 2, 92,223,129, 99, 61,124, 34,192,158, 29, 67,161,255,
45 70, 24,250,164, 39,121,155,197,132,218, 56,102,229,187, 89, 7,
46 219,133,103, 57,186,228, 6, 88, 25, 71,165,251,120, 38,196,154,
47 101, 59,217,135, 4, 90,184,230,167,249, 27, 69,198,152,122, 36,
48 248,166, 68, 26,153,199, 37,123, 58,100,134,216, 91, 5,231,185,
49 140,210, 48,110,237,179, 81, 15, 78, 16,242,172, 47,113,147,205,
50 17, 79,173,243,112, 46,204,146,211,141,111, 49,178,236, 14, 80,
51 175,241, 19, 77,206,144,114, 44,109, 51,209,143, 12, 82,176,238,
52 50,108,142,208, 83, 13,239,177,240,174, 76, 18,145,207, 45,115,
53 202,148,118, 40,171,245, 23, 73, 8, 86,180,234,105, 55,213,139,
54 87, 9,235,181, 54,104,138,212,149,203, 41,119,244,170, 72, 22,
55 233,183, 85, 11,136,214, 52,106, 43,117,151,201, 74, 20,246,168,
56 116, 42,200,150, 21, 75,169,247,182,232, 10, 84,215,137,107, 53};
58 //--------------------------------------------------------------------------
59 // Reset crc16 to the value passed in
61 // 'reset' - data to set crc16 to.
63 void setcrc16(int portnum, ushort reset)
65 utilcrc16[portnum] = reset;
69 //--------------------------------------------------------------------------
70 // Reset crc8 to the value passed in
72 // 'portnum' - number 0 to MAX_PORTNUM-1. This number is provided to
73 // indicate the symbolic port number.
74 // 'reset' - data to set crc8 to
76 void setcrc8(int portnum, uchar reset)
78 utilcrc8[portnum] = reset;
82 //--------------------------------------------------------------------------
83 // Calculate a new CRC16 from the input data shorteger. Return the current
84 // CRC16 and also update the global variable CRC16.
86 // 'portnum' - number 0 to MAX_PORTNUM-1. This number is provided to
87 // indicate the symbolic port number.
88 // 'data' - data to perform a CRC16 on
90 // Returns: the current CRC16
92 ushort docrc16(int portnum, ushort data)
94 data = (data ^ (utilcrc16[portnum] & 0xff)) & 0xff;
95 utilcrc16[portnum] >>= 8;
97 if (oddparity[data & 0xf] ^ oddparity[data >> 4])
98 utilcrc16[portnum] ^= 0xc001;
101 utilcrc16[portnum] ^= data;
103 utilcrc16[portnum] ^= data;
105 return utilcrc16[portnum];
108 //--------------------------------------------------------------------------
109 // Update the Dallas Semiconductor One Wire CRC (utilcrc8) from the global
110 // variable utilcrc8 and the argument.
112 // 'portnum' - number 0 to MAX_PORTNUM-1. This number is provided to
113 // indicate the symbolic port number.
114 // 'x' - data byte to calculate the 8 bit crc from
116 // Returns: the updated utilcrc8.
118 uchar docrc8(int portnum, uchar x)
120 utilcrc8[portnum] = dscrc_table[utilcrc8[portnum] ^ x];
121 return utilcrc8[portnum];