Publication 1756-UM514B-EN-P - February 2003
Using the 1756-DHRIO Module in Remote I/O Applications 8-11
Setting the Data Exchange
Rate Between the
1756-DHRIO Module
and a Controller
The following sections describe the process of setting the Requested
Packet Interval (RPI) for data exchanges between the 1756-DHRIO
module and the ControlLogix controller. An RPI must be set for both
the remote I/O scanner status connection and each adapter
connection.
Requested Packet Interval (RPI)
This interval specifies the rate at which the 1756-DHRIO module and
the ControlLogix controller produce data. The time ranges from 3mS
to 750mS and is sent to the module with all other configuration
parameters. When the specified time frame elapses, the 1756-DHRIO
module and the ControlLogix controller produce data for each other.
RIO Scanner Status Update Rate With the 1756-DHRIO in a Local
Chassis
When a module resides in the same chassis as the owner controller,
the RPI affects how and when the module produces link status and
consumes the controller status. The rate at which the status is
exchanged is equal to the RPI.
RIO Scanner Status Update Rate With the 1756-DHRIO Module in
a Remote Chassis
If a module physically resides in a chassis other than that of its
owner-controller (i.e. a remote chassis connected via ControlNet), the
rate at which the status is exchanged is equal to the RPI + 2 x
[Network Update Time (NUT)].
TIP
To maximize notification of the module status, we
recommend setting the 1756-DHRIO module’s RPI
value equal to the RPI used in the adapter
connections.
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