Pilot Communications SPM93 - Modes of Transmission; Description of the Modbus Packet Structure; Address Field

29
9.2.2 Modes of Transmission
Modbus protocol supports ASCII and RTU modes of transmissions. The SPM93
supports only the RTU mode of transmission with 8 data bits, no parity, and 1
stop bit.
9.2.3 Description of the Modbus Packet Structure
Every Modbus packet consists of four fields:
1) The Address Field
2) The Function Field
3) The Data Field
4) The Error Check Field
9.2.3.1 Address Field
The Address Field is 1-byte long and identifies which Slave device the packet is for.
Valid addresses range between 1 and 247. The Slave device whose address
matches the value in this field will perform the command specified in the Packet.
The respond packet of Slave should be its own address.