Owner manual

2 SureCross

DX80 Modbus Register Definitions

Modbus distinguishes between inputs and outputs and between bit-addressable and word addressable data items.

For more information, please refer to www.modbus.org. A less documented but commonly used method to separate the

data types is using a mapped address structure.

Reference Description

0xxxx Read/Write Discrete Output. Drives output data to a discrete output point.

1xxxx Read Discrete Inputs. Controlled by the corresponding discrete input point.

3xxxx Read Input Registers. Contains a 16-bit number received from an external source, like an analog

signal.

4xxxx Read/Write Output or Holding Registers. Stores 16-bits of numerical data (binary or decimal), or

sends the data to an output point.

The xxxx represents the four-digit address location in user data memory. Because function codes generally denote the

leading character, the leading character is omitted from the address specifier for a given function. The leading character

also identifies the I/O data type. The SureCross DX80 Modbus registers are all holding registers 4xxxx using the mapped

address structure.

2.1 Modbus Holding Registers

There are sixteen Modbus holding registers for each SureCross

™

device. Calculate the holding register number for each

device using the equation: Register number = I/O# + (Node# × 16).

Because the Gateway is always first, at Node 0, the Gateway’s holding registers are registers 1 through 16. Registers for

Node 1 are 17 through 32, as shown in the Modbus Holding Register table below. Although only 10 Nodes are shown, the

table can continue for as many Nodes as are used in a given network.

Using the equation or the Modbus Holding Registers table, the register number for I/O point 15 for Node 7 is 127.

Modbus Holding Registers

I/O Pt. Gateway Node 1 Node 2 Node 3 Node 4 Node 5 Node 6 Node 7 Node 8

1 1 17 33 49 65 81 97 113 129

2 2 18 34 50 66 82 98 114 130

3 3 19 35 51 67 83 99 115 131

4 4 20 36 52 68 84 100 116 132

5 5 21 37 53 69 85 101 117 133

6 6 22 38 54 70 86 102 118 134

7 7 23 39 55 71 87 103 119 135

8 8 24 40 56 72 88 104 120 136

9 9 25 41 57 73 89 105 121 137

10 10 26 42 58 74 90 106 122 138

11 11 27 43 59 75 91 107 123 139

12 12 28 44 60 76 92 108 124 140

13 13 29 45 61 77 93 109 125 141

14 14 30 46 62 78 94 110 126 142

15 15 31 47 63 79 95 111 127 143

16 16 32 48 64 80 96 112 128 144

Host Controller Systems