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Configuring the MES1A/B
Manual Documentation Number: MES1A/MES1B-2106m PN7138-rev001
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0B (hex) - Target Device Failed to Respond
• If the slave did not answer, or the answer contained a CRC error
• If a TCP socket is open, but no response is received within the defined
message timeout period
• If a TCP socket is open, but the remote Modbus TCP slave/server
returned exception 0B (hex)
Disable Modbus/TCP Pipeline
Typically a Modbus master issues a query and waits for a response before
issuing another. However, when using Modbus/TCP, multiple queries can be
issued and the MES1A/B will buffer them in a “pipeline”. The MES1A/B
can fetch each query one at a time, and respond. In some situations this is
useful, but in others the sequence of query/response can get out of sync
(especially if any queries or responses are lost). The Disable Modbus/TCP
Pipeline setting allows you to decide how you want the system to operate.
• Setting this field to 1 = No configures the MES1A/B to allow pipeline
operation. This is considered the safest default setting. It is
recommended that you choose this option unless you are experiencing
problems.
• Setting this field to 2 = Yes configures the MES1A/B to always fetch the
latest request from the TCP buffer (discarding all older requests).
Character Timeout
Although Modbus/RTU specifies a 3.5 character time out period between
characters, the Character Timeout field allows you to set a custom value for
this field.
• If you set this field to 0, the MES1A/B will automatically calculate a
minimum timeout based on the baud rate being used.
• Although you can set this field to any value between 1 milliseconds and
6959 milliseconds, a recommended safe value for general use is about 50
milliseconds (which is the default value).
Message Timeout
The Message Timeout field allows you to set the timeout period for
responses from a connected slave to any value between 200 milliseconds and
65000 milliseconds. The default value is 5000 milliseconds.