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.