Allen-Bradley 1785-L80B PLC-5/80 Enhanced Processor

1785-L80B Allen-Bradley PLC-5 Enhanced Controller

Product Introduction

The 1785-L80B is a high-capacity programmable logic controller from Allen-Bradley's PLC-5 enhanced series. This processor provides 100,000 words of embedded user memory, giving you ample space for large programs and complex data tables. Consequently, it suits demanding applications such as material handling, packaging lines, and process control.

This controller stands out with its extensive communication capabilities. It includes four multifunctional ports (Channel 1A, 1B, 2A, and 2B). Each port can operate as a remote I/O scanner, a remote I/O adapter, or a DH+ communication interface. Additionally, a dedicated serial port (Channel 0) supports RS-232, RS-422A, and RS-423 standards. This versatility allows seamless integration with a wide variety of field devices.

Redundancy support is another key feature of the 1785-L80B. You can configure two processors in a hot-standby arrangement for critical processes. This ensures minimal downtime and maximum system availability. For these reasons, the 1785-L80B is a preferred choice for high-reliability installations.

Technical Specifications

The 1785-L80B delivers impressive memory capacity. Its 100-kiloword user memory supports extensive ladder logic, SFC programs, and data storage. For additional program backup, you can install EEPROM modules such as the 1785-ME16, 1785-ME32, 1785-ME64, or 1785-M100. These modules provide non-volatile storage directly on the front panel.

I/O capacity matches the needs of large systems. This processor handles up to 3072 total I/O points in any mix. When using complementary addressing, it manages 3072 inputs and 3072 outputs simultaneously. Analog I/O capacity also reaches 3072 channels, supporting process-intensive applications.

The 1785-L80B supports up to 93 I/O chassis in total. Each remote I/O link handles a maximum of 32 chassis. This scalability makes it suitable for large factories with geographically distributed equipment.

Power consumption is efficient for its class. The controller draws 2.3 Amps at 5 Volts from the backplane, with total power dissipation of 12 Watts. This allows integration without overloading the chassis power supply.

Communication Interfaces

The four DH+/Remote I/O ports provide exceptional flexibility. Each port (1A, 1B, 2A, 2B) can be independently configured for different roles. In scanner mode, the 1785-L80B acts as a supervisory controller for remote adapters and I/O modules. It reads inputs and writes outputs efficiently across the link.

In adapter mode, the 1785-L80B manages its local I/O while following commands from a supervisory controller. This mode is useful in hierarchical architectures where multiple controllers share I/O resources.

DH+ networking enables peer-to-peer communication with other PLC-5 controllers and higher-level systems. This link supports remote programming and monitoring of multiple controllers simultaneously. Cable length depends on speed: up to 3048 meters at 57.6 kbit/s, or 762 meters at 230.4 kbit/s. All devices on the network must operate at the same baud rate.

The serial port (Channel 0) uses a 25-pin optically isolated connector. It supports ASCII and DF1 protocols, including full-duplex and half-duplex master/slave modes. A green LED indicates active communication on this port.

Additionally, two 8-pin mini-DIN connectors provide programming terminal access parallel to Channels 1A and 2A. This simplifies connecting a programming terminal without disrupting the primary network.

Status Indicators and Diagnostics

The 1785-L80B features comprehensive front-panel LEDs. The BATT indicator monitors the 1770-XYC battery status. A lit LED alerts you when battery replacement is needed to prevent memory loss.

The PROC indicator shows the controller's operating state. Green indicates RUN mode. A red light signals a fault condition requiring attention. This quick visual reference helps technicians diagnose issues rapidly.

The FORCE indicator glows amber when I/O forces are active. This warns operators that override conditions are present, reducing the risk of unexpected machine behavior.

The COMM indicator reflects Channel 0 serial communication activity. Each of the four DH+/RIO channels (1A, 1B, 2A, 2B) also has a dedicated status LED. These indicators assist in troubleshooting network connectivity and link integrity.

Redundancy and High Availability

The 1785-L80B supports controller redundancy for mission-critical applications. You can pair two processors in a hot-standby configuration. If the primary controller fails, the secondary takes over automatically with minimal interruption.

This redundancy feature is essential for continuous processes such as chemical production, power generation, and water treatment. The 1785-L80B ensures your system remains operational even during unexpected hardware issues.

Installation and Compatibility

Installing the 1785-L80B is straightforward. It fits into standard PLC-5 chassis including the 1771-A1B, 1771-A2B, 1771-A3B, 1771-A3B1, and 1771-A4B models. Ensure the chassis backplane provides sufficient power for the 2.3 Amp draw at 5 Volts.

Compatible power supplies include the 1770-P1, 1770-P45, 1770-P5, 1771-PE, 1771-P4S1, 1771-P6S1, 1771-P4R, and 1771-P6R. These power supplies provide the necessary voltages for reliable operation.

When configuring the system, use the programming software to set communication parameters for each channel. Assign node addresses, select baud rates, and choose operating modes (scanner, adapter, or DH+) based on your network topology.

For expanded I/O, the 1785-L80B connects to remote I/O racks using standard cables. It also configures I/O modules and extension racks seamlessly. This simplifies system expansion and maintenance.

Packaging List

• Allen-Bradley 1785-L80B PLC-5/80 enhanced processor (1 unit)

• Battery (1770-XYC type, installed)

• Keyswitch (attached)

• Installation guide (printed)

• Factory packaging with anti-static protection

Optional EEPROM modules (1785-ME16, 1785-ME32, 1785-ME64, 1785-M100) are sold separately.

Frequently Asked Questions

Q1: What is the maximum user memory of the 1785-L80B?
A: The 1785-L80B provides 100 kilowords of embedded user memory. You can expand program storage using EEPROM modules such as the 1785-ME16, 1785-ME32, 1785-ME64, or 1785-M100.

Q2: How many I/O chassis can the 1785-L80B support?
A: This processor supports up to 93 I/O chassis in total. However, each remote I/O link limits you to 32 chassis per link.

Q3: Does the 1785-L80B support controller redundancy?
A: Yes, the 1785-L80B supports hot-standby redundancy. Two processors can be paired for automatic failover in critical applications.

Q4: What communication protocols does the 1785-L80B support?
A: The 1785-L80B supports DF1, ASCII, Data Highway Plus (DH+), and Remote I/O (RIO) protocols across its four multifunctional ports and serial interface.

Q5: Which chassis are compatible with the 1785-L80B?
A: Compatible chassis include the 1771-A1B, 1771-A2B, 1771-A3B, 1771-A3B1, and 1771-A4B models. Supported power supplies include 1770-P1, 1770-P45, 1771-PE, 1771-P4R, and 1771-P6R.