Honeywell VCR DCP200 Manuel D’Utilisation

DCP200 Profile Controller & Recorder - Product Manual

Page 80

Serial Communications

51-52-25-150, Issue 1 – April 2009

Modbus defines several function types. The following types are supported by this instrument:

03 / 04

Read Holding/Input registers

Read current binary value of specified number of 
parameters at given address. Up to 64 parameters 
can be accessed with one Query.

06

Write Single Register

Writes two bytes to a specified word address. 

08

Diagnostics

Used for loopback test only.

16 (0x10 hex)

Write Multiple Registers

Writes up to 253 bytes of data to the specified 
address range.

23 (0x17 hex)

Read/Write Multiple Registers

Reads and Writes 253 bytes of data to the specified 
address ranges.

The following is interpreted from the Modbus Protocol Description obtainable from  
http://www.modbus.org/. Refer to that document if clarification is required.

In the function descriptions below, the preceding device address value is assumed, as is the 
correctly formed two-byte CRC value at the end of the QUERY and RESPONSE frames.

Reads current binary value of data at the specified word addresses.

03 / 04

HI

LO

HI

LO

03 / 04

HI

LO

HI

LO

In the response the “Number of Bytes” indicates the number of data bytes read from the 
instrument. E.g. if 5 words are read, the count will be 10 (A hex). The maximum number of
words that can be read is 64. If a parameter does not exist at one of the addresses read, 
then a value of 0000h is returned for that word.