Data Highway Plus Protocol

Data Highway Plus is a networking system made by the Allen-Bradley Company (now called Rockwell Automation). It is a networking protocol suite for manufacturing automation. It is normal in networking innovation to express protocols in layers of capacities. The Data Highway Plus suite contains three layers. These are the physical layer, the data join layer and the application layer.

The Data Highway Plus protocol give directions to a PLC (programmable logic controller) that controls a bit of modern apparatus. The protocol indicates a message packet format to convey these commands. The message header contains a byte each to clarify the source of the message, the destination of the message and the command to be executed. There is additionally, alternatively, a capacity byte. The answer to this command will answer in a packet headed by source, destination and summon bytes, trailed by maybe a couple bytes for status codes. Summons and reactions are coordinated together by a TNS (“transaction”) code. The reaction to a summon will contain the TNS of the charge to which it is an answer. Both the summon message and the reaction message can alternatively contain a data segment.

Data Highway Plus Interfaces

Cat. No. Function Communication Interface Communication Rates
Supported (bit/s)
Current Load
1784-PKTX, 1784-PKTXD PKTx Communication Card§ Performs data transmission, management, and local network diagnostics for PLC-5 processors over DH+ networks. The 1784-PKTXD has two ports for DH+ communication. 1770-CD (Belden #9463) • 762 m (2,500 ft) @ 230,400 bit/s
• 1,524 m (5,000 ft) @ 115,200 bit/s
• 3,048 m (10,000 ft) @ 57,600 bit/s
0.8A @ 5V DC
1784-U2DHP USB to Data Highway Plus cable Program PLC-5 or SLC 5/04 processors using a personal computer and RSLogix 5 or 500 Programming Software; lets a DH+ host with RSLinx software communicate directly with DH+ stations USB port on computer to 8-pin mini-DIN connector on controller. • DH+: 57,600; 115,200; 230,400 Powered through USB
1756-DHRIO DH+/RIO Communication Interface Module • Provides gateway functionality between ControlNet, Ethernet, and DH+ networks
• Provides scanner functionality to Universal Remote I/O links adapters
2 ports: DH+ or Universal Remote I/O • For DH+: 57,600, 115,200, or 230,400
• For Universal Remote I/O: 57,600, 115,200, or 230,400
• 710 mA @ 5V DC
• 1.7 mA @ 24V DC
1771-AF Fiber-Optic Converter Module Allows DH+ and Remote I/O signals to travel over fiber-optic cable for routing through electrically noisy environments; converts twinax electrical signals to light (for transmission over fiber-optic cable), and then converts the light back to electrical signals (for transmission on twinax) • Twinax
• Fiber-optic pre-terminated cables, 1771- PT2 (75 m)
57,600 and 115,200 600 mA
1771-AF1 Fiber Optic Converter (Stand-alone) 1A