For Modbus protocol, the RTU port and the node number of the targeted equipment determine the net and node fields:
Register Address |
Description |
Size / Limitation |
Catalyst SNA |
---|---|---|---|
0xxxx |
Coil number xxxx |
1-bit |
1*node*0xxxx |
1xxxx |
Input number xxxx |
1-bit |
1*node*1xxxx |
3xxxx |
Input register number xxxx |
16-bit |
1*node*3xxxx |
4xxxx |
Output register number xxxx |
16-bit |
1*node*4xxxx |
5xxxx |
Floating Point register |
32-bit |
1*node*5xxxx |
Note: The 5x and 4x references share the same data space. That is, an address of the form 5nnnn takes the 32 bits beginning at location 4nnnn and extending through 4nnnn+1. These 32 bits are then interpreted as an IEEE floating point number. |
The following list identifies special issues with regard to this addressing scheme: