Forbes Marshall CODEL EnergyTech 300 Series, Инструкция по установке, пусконаладке и эксплуатации

Страница: 39 / 72

www.codel.co.uk
Page: 39 © 2010 CODEL International Ltd.
CODEL
300
8 Appendix 1
1.25 Standard MODBUS Communication with
CODEL MODBUS
Summary; Using standard MODBUS protocol, function 03 allows a host to obtain
the contents of one or more holding registers in the CODEL MODBUS.
The request frame from the host (typically a DCS or SCADA) defines the relative
address of the first holding register followed by the total number of consecutive
registers to be read.
The response frame from the CODEL ET301 lists the contents of the requested
registers, returning 2 bytes per register with the most significant byte first. A
maximum of 125 registers can be accessed per request.
The formats of the request and response frames are detailed below, where ‘X’ and
‘n’ are hexadecimal variables.
An example of a MODBUS register map is shown below.
01 Address
03 Function code
XX
XX Address of starting register
00
XX Number of consecutive registers
XX
XX CRC
Host Request Frame