About 1785-L80B
The programmable controller 1785-L80B is a central part of each
control system based on the Allen Bradley PLC-5 series. The
1785-L80B connects local, extended, and remote I/O modules on
various communication interfaces into one control system. Four
built-in ports are available on the 1785-L80B controller. The ports
are marked as channel 1A, channel 1B, channel 2A, and channel 2B.
All ports can be configured and used as remote I/O scanners, remote
I/O adapters, and DH+ communication interfaces. DH+ communication
can be used both for remote programming and monitoring of the
1785-L80B and for creating a peer-to-peer communication network
between the various PLC-5 controllers. Remote I/O connection is
used for real-time data exchange between the controller and I/O,
operator interface, and other functions. All four channels on the
1785-L80B can function as remote I/O scanners or remote I/O
communication adapters. Remote I/O scanner mode reads and writes
I/O information between a controller and a remote I/O device. In
this mode, the 1785-L80B is a supervisory controller for other
controllers that are in adapter mode and for remote I/O adapter
modules. When any of the four channels 1A, 1B, 2A, or 2B, function
in remote I/O adapter mode, the controller monitors its
controller-resident local I/O while communicating with the
supervisory controller via a remote link.
On the 1785-L80B, the Data Highway Plus (DH+) link can be used on
all four existing channels. DH+ communication can be used for data
transfer to other PLC-5 controllers or other higher-level
components of the control system. The DH+ link can program multiple
PLC-5 controllers. On the front panel of the 1785-L80B controller,
there is a 25-pin connector marked channel 0. This is an optically
isolated EIA RS232C port. Channel 0 supports ASCII and DF1 full and
half-duplex master and half-duplex slave protocols. On the front
panel is a green channel 0 communication indicator light. Beside
channel 0, there are two 8-pin mini-DIN connectors marked as
channel 1A and channel 2A, and there is a DH+ programming terminal
connection parallel to channels 1A and 2A. There are four three-pin
connectors used as communication ports. These three-pin connectors
are used for channel 1A, 1B, 2A, and 2B. All of these ports can
function as remote I/O scanners, remote I/O adapters, or as DH+
communication ports. The maximum cable length for the DH+ link
depends on the transmission rate. It is crucial that all devices on
a DH+ link communicate at the same rate. That length goes from a
maximum 3048m for speed 57.6 kilobits per second, to 762m for a
speed of 230.4 kilobits per second.
The 1785-L80B has several indicators on the front panel for easy
interaction. Indicators display various controller statuses. The
indicator marked BATT displays the status of the battery. The
indicator marked PROC indicates the current controller mode, it is
green when the controller is in RUN mode, and red when something is
wrong. The FORCE indicator is amber when the I/O forces are
enabled. The COMM indicator is linked with channel 0's
communication status. The indicator is green when the channel is
communicating. All four communication channels: 1A, 1B, 2A, and 2B,
have dedicated status indicators.
