Handling broken ethernet/ip i/o connections – Delta RMC151 User Manual
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RMC70/150 and RMCTools User Manual
As soon as the first register is encountered that is not a current or initial variable
register, the guarantee for data consistency no longer applies. Remaining registers in
the I/O block will be processed as time allows on subsequent motion loops, taking up
to a maximum of 10 ms. For this reason, variables should be included first in the
Incoming I/O Data Area of the Indirect Data Map in order to ensure their consistency.
Notice that if commands are mapped to the Indirect Data, the commands will all be
submitted at the same time, after all values have been written.
Other Locations
No data consistency is guaranteed when consuming in other areas (such as axis
parameters). The entire write can take as long as 10 ms, with the write being deferred
to the next control loop at any point as required to meet loop time requirements.
6.8.10.6.4. Handling Broken EtherNet/IP I/O Connections
It is important to detect loss of an EtherNet/IP I/O connection quickly. EtherNet/IP supports a
variable timeout value, which is expressed in terms of Requested Packet Intervals (RPIs). The
RMC supports multipliers ranging from 4x to 512x. The PLC may allow you to select this
timeout multiplier value, or may fix it to a certain value. For example, the ControlLogix
establishes its EtherNet/IP I/O connections with a timeout of 32 RPIs. Therefore, an RPI of 4.0
ms will have a timeout of 32 x 4.0 ms or 128 ms.
When either device in an I/O connection does not receive a packet from the other device for
the timeout interval, it closes the connection and typically indicates this condition to the main
program. The method of indicating this condition depends on the actual device. This topic
describes the methods used by the RMC and several common PLCs.
Handling Broken I/O Connections in the RMC
The RMC has tags that indicate the state of the controlling connection. The user can use
these registers to qualify whether certain operations in the User Programs can be done,
or they can use these registers in the Program Triggers to respond to the change in state
of the controlling connection.
Tag Name
Description
Controlling Connection Active
This bit is set as long as a Controlling Connection is
currently active. If the connection is closed or timed out,
this bit will be cleared.
Controlling Connection Timed Out
This bit is set when a Controlling Connection timed out.
Notice that this is only one method of a controlling
connection being closed (another example is the PLC
intentionally closing it). This bit is cleared when the
Controlling Connection is re-opened. The user can look for
the rising edge of this bit in the Program Triggers to
respond to a time-out.
A time-out can occur when the cable is disconnected, or
when the client is powered off or reset.
Controlling PLC Status
This register indicates the state of the controlling PLC.
This register (DINT data type) can hold one of three
values: Unknown (0), Run (1), and Program (2). The
Unknown state applies whenever no controlling
EtherNet/IP connection is active.
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Delta Computer Systems, Inc.