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2.1
OPERATIONAL OVERVIEW
The Allen-Bradley Remote I/O (RIO) interface is
standard on many PLC-2, 3, and 5 series
programmable logic controllers. The technology
used in the interface and licensed by Allen-Bradley
to BLH enables the DXp-40 transmitter to
communicate weight information to the PLC as if it
were a 1/4 rack of discrete I/O. By using the
standard RIO interface port and representing
weight data as simple discrete I/O, a low cost
reliable communication link between the PLC and
weigh system is established. Standard PLC ladder
logic instructions convert binary weight data to an
integer or floating point weight value without
special software drivers and scan delays that occur
when data block transfers are used. The DXp-40
also communicates status information, diagnostics,
and calibration data to the PLC.
CONFIGURATIONS:
SECTION 2.
The Remote I/O Interface
Figure 2-1. RIO Communication DIP Switch
Settings
One Quarter Rack. The DXp-40 is configured to
act as 1/4 rack of I/O using 2 input words and 2
output words in the PLC's I/O image table. DXp-40
addressing supports racks 1-32. Four DXp-40s
constitute 1 full rack, each using a different starting
quarter. Discrete Transfer, Weight data and operating
status information transmitted through discrete
transfer using the PLC's Remote I10 image table.
Block Transfer, Block data transfers are initiated by
the PLC ladder logic program to obtain more in
depth status, diagnostic, and individual load cell
data.
Word Integrity Is Ensured. The DXp-40 will always
transmit both input image table words intact. To
ensure word integrity on the PLC side, immediate
writes to the output image table should be written
low word first.
2.2
HARDWARE CONFIGURATIONS
Rack address and starting quarter designations are
all configured using a row of DIP switches in the
DXp-40 (Figure 2-1). The DXp-40 is able to be
addressed up to rack number 32. Whenever the
DIP switch settings are changed, the unit must be
reset to allow the processor to read the new switch
settings.
RIO interface baud rate selections are available
through the DXp-40 main menu (Figure 2-2).
Recommended cable lengths are presented in
Figure 2-1.
2-3
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