Delta RMC151 - Manual (Page 466)

RMC70/150 and RMCTools User Manual
Connection Type
The RMC supports three types of I/O connections:
• Input/Output
This connection is bidirectional: the originator (PLC or HMI) produces data consumed
by the RMC and the target (RMC) produces data that is consumed by the originator.
This connection type is also called an Exclusive Owner connection or the controlling
connection. Each RMC can have no more than one Input/Output connection open at a
time.
• Input Only
For this connection type, only the target (RMC) produces data, which is consumed by
the originator (PLC or HMI). The originator will only send a heartbeat packet,
sometimes at a reduced interval (less frequently than the RPI) used to allow the RMC
to identify when the connection is broken.
• Listen Only
This connection type is identical to an Input Only connection type, with one exception:
a Listen Only connection can only exist when one of the other I/O connection types
has been established. That is, a Listen Only connection cannot be established until an
Input/Output or Input Only connection has been established, and conversely when the
last non-Listen-Only connection has been closed or has timed out, the Listen Only
connection will automatically close as well. This connection type is the least-frequently
used. This connection type is not supported by RMC firmware 3.40.x or older.
Of these three, the Input/Output connection type is by far the most commonly used. The
other two are generally only used when multiple I/O connections are used. See the
Multiple EtherNet/IP I/O Connections topic for details.
When using the RMC’s EDS file in your EtherNet/IP configuration tool, you should be able
to select the I/O connection type from a list. Notice that in addition to the three listed
above, you may also see Input/Output with Config and Input Only with Config.
These connection types are generally not used. For details on these connection types, see
the Configuration Data section below. If you are using a Generic EDS File (as required by
RSLogix 5000 as of this writing), see the Using a Generic EDS File section below.
Requested Packet Interval (RPI)
EtherNet/IP I/O sends data between the communicating devices at the Requested
Packet Interval (RPI). The RPI is configured in the EtherNet/IP controller (for example,
RSLogix 5000), not in RMCTools. The RMC supports the following RPIs, based on the
number of simultaneous I/O connections established (see the Multiple EtherNet/IP I/O
Connections topic):
I/O
Connections Minimum RPI Typical RPI Maximum RPI
1 (typical) 2 ms 20 ms 10,000 ms
2 3 ms 20 ms 10,000 ms
3 4 ms 20 ms 10,000 ms
4 4 ms 20 ms 10,000 ms
Also, the RPI must be both an integer number of milliseconds and a multiple of the RMC’s
Loop Time. For example, an RPI of 9 ms would not be allowed for a loop time of 2 ms or 4
ms, but would be for 1 ms or lower loop times.
Delta recommends using the slowest RPI that meets the requirements of your application
in order to reduce network requirements. See the EtherNet/IP I/O Performance topic for
more details.
Multicast vs. Point-to-Point (Unicast)
446 Delta Computer Systems, Inc.