AN-X2-MOD-MON Page
27
Exchanging Scheduled Data with a ControlLogix
A Modicon S908 remote I/O network can contain up to 2048 words of input data and
2048 words of output data (32 drops x 64 words per drop).
Each scheduled connection with a ControlLogix contains at most 250 words of input data
and 248 words of output data. In order to be able to monitor the largest possible Modicon
network, the AN-X2-MOD-MON module supports multiple scheduled connections with a
ControlLogix processor over Ethernet.
The AN-X2-MOD-MON module behaves like a 17-slot ControlLogix rack with an
ENBT/A module in slot 16 and generic modules in slots 0 to 15.
A ControlLogix processor can open scheduled connections to each of these 16 generic
modules. Each scheduled connection consists of up to 248 words of output data from the
ControlLogix processor to the AN-X and up to 250 words of input data from the AN-X to
the ControlLogix processor. Since all Modicon I/O is mapped to scheduled input data,
you usually set the output size of the scheduled connections to the minimum allowed
value, 1.
Each connection can have its own RPI, up to 750 ms.
In general, you should try to keep the number of connections as small as possible. There
is significant overhead in opening and maintaining each connection.
You map the inputs and outputs for the Modicon I/O modules on the S908 network to
input data in these scheduled connections. AN-X can create the mappings automatically
or you can create a mapping configuration file manually.
You can also have AN-X create the mapping file automatically, then edit the file to better
suit your application. For example, in order to make the most efficient use of the available
Ethernet bandwidth, you can organize the data so that items that update quickly are
mapped to connections with short RPIs and items that are less time critical are mapped to
connections with longer RPIs.
In addition, the AN-X module has diagnostic data that can be mapped to ControlLogix
scheduled input data.
The mapping file can also contain options that apply to the entire configuration.
Configuring the AN-X in RSLogix 5000
The AN-X2-MOD-MON emulates a 17-slot 1756 chassis with an ENBT/A in slot 16 and
up to 16 generic modules in slots 0 to 15.
Connections to slots 0 to 14 are used for I/O data; the connection to slot 15 is reserved for
diagnostic data (see page 32). For large networks, AN-X may assign some of the
diagnostic data to connection 14 if the disgnostics overflow connection 15.
To configure the AN-X2-MOD-MON in RSLogix 5000:
1.
Right click on the ControlLogix Ethernet bridge module that will be
communicating with the AN-X and select
Add Module
. Add a 1756-ENBT/A
module.
