Determining Connections For I/O Modules; Direct Connections For I/O Modules - Allen-Bradley ControlLogix User Manual

A-2 Allocating Communication Connections
Device
1756-L1
1756 I/O modules ControlLogix I/O modules
1756-CNB
1756-CNBR
1756-ENET
1756-DHRIO
1756-DNB
Determining Connections
for I/O Modules
1756-6.5.3 - December 1999
These modules support the following number of connections:
Description
Logix5550 Controller
ControlLogix ControlNet
Interface module
ControlLogix Ethernet Bridge
ControlLogix DH+ Bridge and
Remote I/O Scanner
ControlLogix DeviceNet Bridge 2 connections
All I/O modules can have a direct, bidirectional connection to the
Logix5550 controller. A 1756-CNB ControlNet interface module supports
the ability to organize a chassis of digital I/O modules into one bidirectional
connection (rack connection), rather than requiring a direct bidirectional
connection for each individual I/O module.
You can configure these types of connections to these modules:
A Logix5550 connection to
local I/O
remote I/O

Direct connections for I/O modules

A direct connection is a real-time, data transfer link between the Logix5550
controller and an I/O module. The Logix5550 controller maintains and
monitors the connection between the controller and the I/O module. Any
break in the connection, such as a module fault or the removal of a module
from the chassis while under power, causes the controller to set fault status
bits in the data area associated with the module.
If a Logix5550 controller has a module configuration that references a slot
in the control system, the controller periodically checks for the presence of
a device in that slot. When a device's presence is detected there, the
controller automatically sends the module configuration.
Connections
250 connections
16 connections
64 connections
64 TCP/IP connections
48 ControlLogix connections maximum per 1 TCP/IP connection
128 ControlLogix connections maximum per module
The Ethernet module also supports 128 in and 128 out
unscheduled ControlLogix connections. Unscheduled connections
within a TCP/IP connection do not count toward the total of 48
possible ControlLogix connections.
32 connections per DH+ channel
32 rack connections and 16 block-transfer connections per
remote I/O channel
Can use this connection type
direct connection only
direct connection
or
rack optimized connection