Rockwell Automation 1794-ASB/E Remote I/O Adapter Module User Manual - Manual (Page 36)

3–2 Communicating with FLEX I/O Modules
Publication 1794ĆUM009D-EN-P - April 2004
The 1794-ASB series E adapter supports 5 different modes of
addressing: standard, compact, complementary, standard–32 and
complementary–32.
For digital modules, the mode of addressing determines what type of
data is available to the processor from the module.
•
standard addressing – input and output data is available for each
digital module connected to the adapter
•
compact addressing – either input or output data (not both) is
available for each digital module connected to the adapter
•
complementary addressing – either input or output data (not both)
is available for each digital module connected to the adapter
Analog modules can be used in any mode of addressing with no loss
of data because data is not stored in the input and output image table,
with the exception of the MCB and MSB. Analog data is stored in
BTW and BTR data files.
The following table helps you to select an addressing mode based on
the kind of modules you want to use, and the features you need from
those modules. The table also lists both advantages and
disadvantages of using each addressing type.
Addressing Mode Use this addressing scheme when: Advantages Disadvantages
Standard
•
you need full FLEXI/O module
functionality, including combination
modules (1794ĆIB10XOB6), settable
input delay times on input modules
(1794ĆIB16, ĆIB8S), and fuse blown
indication (1794ĆOB8EP) for
example. Will work with 32-pt.
modules with 16 in and 16 out
(1794-IB16XOB16P).
•
User has access to 1 word of input, 1
word of output for each digital module.
•
Eight modules equal 1 logical rack.
•
No restrictions on module placement
•
Maximum use of configuration/status and
combination modules
•
Inefficient I/O image table
utilization
Compact
•
you don't need full FLEXI/O module
functionality, including combination
modules (1794ĆIB10XOB6), settable
input delay times on input modules
(1794ĆIB16, ĆIB8S), and fuse blown
indication (1794ĆOB8EP), for
example.
•
you can locate equal numbers of
input and output modules in a single
chassis
•
Eight 8 point modules equal 1/4 logical
racks (when input and output modules are
installed in alternate slots).
•
Eight 16 point modules equal 1/2 logical
racks (when input and output modules are
installed in alternate slots).
•
Provides maximum use of I/O image table
by a single FLEXchassis (when input and
output modules are installed in alternate
slots).
•
You must configure all modules
in the chassis as either 8Ćpoint
orĆ16 point.
•
No combination modules
allowed
•
Configuration/status data is not
accessible to user
Addressing I/O