Spectrasensors OXY5500, Operator'S Manual, Page: 89 / 140

Modbus Communication
OXY5500 Operator’s Manual 4
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3
Boolean
Boolean registers are 16bit int32 registers with only 0 and 1 as allowed values.
Error response
The error response follows the Modbus definition, but only four exception codes
are implemented:
•
1 (Illegal function): An unsupported function code was used.
•
2 (Illegal data address): The requested register is either not available
or write-protected.
•
3 (Illegal data value): The value could not be set. The value was out
of range. The last correct value will be restored.
•
6 (Slave device busy): This code appears if an active USB connection
(communication via software is active) is connected.
Different Communication Channels
The OXY5500 has multiple ways to read and set its settings and measurement
values:
•
Modbus Communication
• RS-485
• RS-232
• Ethernet
•
USB Service Port
•
Via keypad and LCD
All options share the same fundamental memory. Changing the settings via one
communication channel will alter the expected result on another channel.
Recommendation
One channel should be used to set up the device completely. As the device will
save every setting and allows immediate checking of the results, it is
recommended to do this via keypad and LCD and to use the other channels as
simple data-polling options.
A register holds always exactly 2 characters. Unused bytes are
filled with zeros (ASCII: 0x00).