Technical Specifications

FAQ

1. What is the main function of the Allen Bradley 1784-U2DHP?
The Allen Bradley 1784-U2DHP is a USB-to-Data Highway Plus (DH+) communication adapter designed to connect a modern computer to an Allen-Bradley DH+ industrial network. It provides a practical communication path for applications such as PLC programming, controller monitoring, troubleshooting, configuration, and data access. The adapter is particularly useful when a computer does not have a native DH+ interface but needs to communicate with legacy Allen-Bradley control equipment.

2. What DH+ communication speeds does the 1784-U2DHP support?
The 1784-U2DHP supports three commonly used DH+ communication rates: 57.6 Kbps, 115.2 Kbps, and 230.4 Kbps. The selected communication rate must match the configuration of the DH+ network and connected devices. If the adapter and PLC network use different communication rates, the computer will not be able to establish normal communication with the controller. The communication rate is selected using the hardware settings provided on the adapter.

3. What type of PLC systems can be accessed using the 1784-U2DHP?
The 1784-U2DHP is intended for Allen-Bradley control systems that communicate through the Data Highway Plus network. It can be used with compatible PLC-5 and SLC control systems that provide DH+ communication. Before connecting the adapter, the controller model, DH+ port, node address, communication rate, and software compatibility should be checked. This is especially important when working with older PLC installations where different controller generations may use different communication configurations.

4. Does the 1784-U2DHP require an external power supply?
No separate external power supply is normally required. The 1784-U2DHP receives its operating power through the computer’s USB connection. The adapter operates from a nominal 5.00 V DC USB supply and has a typical current requirement of approximately 125 mA. This USB-powered design simplifies field service because technicians do not need to install a separate power supply simply to establish a temporary programming or diagnostic connection with the DH+ network.

5. How should the DH+ communication rate be configured on the 1784-U2DHP?
The DH+ communication rate must be configured to match the rate used by the target DH+ network. The available settings are 57.6 Kbps, 115.2 Kbps, and 230.4 Kbps. Before attempting communication, verify the existing PLC and DH+ network configuration and then set the adapter accordingly. If the communication setting is changed, disconnecting and reconnecting the USB connection may be necessary so that the adapter initializes with the updated configuration.

6. What software can be used with the Allen Bradley 1784-U2DHP?
The adapter is commonly used with RSLinx Classic and compatible Rockwell Automation programming and communication software. After the appropriate device driver is installed, the computer can recognize the USB adapter and use it as a communication path to the DH+ network. In a PLC maintenance application, the adapter can provide access for programming, controller status monitoring, online diagnostics, and other supported communication functions. The specific software version should be checked for compatibility with the computer operating system and controller being serviced.

7. Why does the 1784-U2DHP fail to establish communication with a DH+ PLC?
Several conditions can prevent successful communication. First, check that the USB connection is recognized correctly by the computer and that the adapter is properly initialized. Next, verify the DH+ cable connection, node address, network communication rate, and PLC operating status. The communication driver in RSLinx should also be configured for the correct adapter and communication path. If the DH+ network uses a different baud rate from the adapter, communication will fail even when the physical wiring is correct. For intermittent communication, inspect the DH+ cabling, connectors, termination, grounding, and other devices connected to the network.

8. Can the 1784-U2DHP be used for PLC programming, monitoring, and troubleshooting?
Yes. The 1784-U2DHP is suitable for a range of maintenance and engineering tasks involving compatible DH+ controllers. A technician can use the adapter to establish an online connection for PLC program access, controller monitoring, communication diagnostics, and troubleshooting. It is particularly useful when servicing legacy control systems where the original programming computer or dedicated DH+ interface is no longer available. When using the adapter in an operating plant, the technician should verify the correct controller and communication path before going online to avoid making unintended changes to the control system.