Allen-Bradley 1794ASB Series B User Manual

3–4 Communicating with FLEX I/O Modules
Publication 17946.5.3 - May 1996
After the rack size has been determined by the remote I/O adapter,
the data from the modules must be mapped into the data tables.
Mapping of data into the data table is different for discrete digital
and analog modules.
Data transfer to and from the remote I/O adapter and discrete digital
modules occurs every flexbus scan. This data is mapped into the
input/output image table.
The remote I/O adapter transfers data to analog I/O modules (block
transfer write) and from analog I/O modules (block transfer read)
using BTW and BTR instructions in your ladder diagram program.
This data is mapped to the data files selected in the ladder logic
block transfer instructions.
The adapter identifies the type of module in each base unit at
powerup, and stores this information for later use, if necessary.
Important: If you are changing your configuration, you must power
down, then power back up after changing a module type
in a terminal base unit.
!
ATTENTION: FLEX I/O modules do not support
complementary I/O. Do not attempt to use the
complementary image table word of a module. The
complementary word is reserved for use by the
module.
!
ATTENTION: Do not use the auto-config feature of
6200 software when using a PLC-3 processor with
1775-S4A or 1775-S4B scanner modules. If you do an
auto-config for a scanner channel containing 1 or more
1794-ASB adapters with that configuration, the
adapters may not show up in the scan list for that
scanner channel. Manually insert these adapters into
the scan list for the scanner.
!
ATTENTION: If the adapter is powered up before
analog modules, the adapter will not recognize the
analog module. Make certain that analog modules are
installed and powered up before or simultaneously with
the remote I/O adapter. If the adapter does not establish
communication with the analog module, cycle power to
the adapter.
Discrete I/O Modules
The adapter determines what type of module is installed in the
terminal base unit. If the module is a discrete module, the adapter
will read 1 word of input and 1 word of output data.
Mapping Data into the
Image Tables

Allen-Bradley 1794ASB Series B Specifications

General

Brand	Allen-Bradley
Model	1794ASB Series B
Category	Adapter
Language	English