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5. Gateway Initialization and Diagnostics
The correct use of this status word by the DeviceNet master, to read a diagnostic generated by the gateway,
goes through the following steps:
• Checking of (ABC_HS_SEND ≠ FB_HS_CONFIRM).
• Reading of the value of ABC_DU to determine whether all of the Modbus input data are up-to-date.
• Reading of the value of the “Periodicity of Modbus exchanges” bit to determine whether the periodicity of
the Modbus communications has been maintained.
• Reading of the values of EC and ED to check for any error detected by the gateway on the Modbus
network (see table below).
• Copying of the value of the ABC_HS_SEND bit to the FB_HS_CONFIRM bit.
This last step is essential because it allows the gateway to transmit a future diagnostic! Even if you do not wish
to read the content of the gateway’s status word, it is preferable to automate this step in your DeviceNet master
software.
The values of the EC and ED fields are described in the table below:
EC Description of the error ED Notes
2#0000 Re-transmissions on the
Modbus network
Number of re-
transmissions (1)
Total number of re-transmissions carried out
on the sub-network, for all slaves.
2#0001 A Modbus slave is missing Address of the missing
Modbus slave
—
2#0010 Several Modbus slaves
are missing
——
2#0011 Excessive data in a
Modbus response
Address of the Modbus
slave involved
This error occurs when the gateway receives too
much data in the response sent by one of its
Modbus slaves.
2#0100 Unknown Modbus error Address of the Modbus
slave involved
—
(1) The re-transmission counter used to signal this error is not reset when the gateway generates this error
code. If there are recurrent communication problems on the Modbus network, the gateway will generate this
same diagnostic repeatedly, so as to tell the DeviceNet master the total number of re-transmissions carried
out as often as possible. This counter is reset when its value exceeds its maximum value (counter modulo
256: 16#FF Æ 16#00).