Technical Specifications

Main Features and Advantages

Deterministic data sharing instead of message passing: The Reliance Electric 57C404C​ does not exchange request-and-reply messages in the way a modern fieldbus does. Every module holds a complete dual-port image of the entire network’s data, and the master continuously refreshes that image across all drops. An application task in one rack therefore reads a variable produced in another rack by simply referencing the register location where that variable lives — no messaging code, no handshaking, no polling logic in the user program. With a worst-case update of 2.99 ms per drop, this gives the tightly coupled behaviour of a single large controller while the hardware is physically distributed along a production line.

Communication load removed from the processors: Network operation on the Reliance Electric 57C404C​ is handled by a dedicated 4 MHz CPU with DMA and serial I/O, running its own firmware. All application data is transmitted and received by the module’s own processor, which means the rack’s main Processor modules pay no communication penalty and remain fully available for control tasks. At power-up the module runs self-diagnostics across its CPU, EPROM, RAM, serial I/O, memory management unit and dual-port memory, writing progress codes to the 7-segment display and halting with a specific code if a test fails.

Diagnostics designed for a technician, not a laptop: The faceplate carries a 7-segment LED that displays registered error codes and a green status lamp that indicates whether the module is operational or should be replaced. The 25-pin MONITOR port provides an RS-232C asynchronous link at 1200 baud, so any ASCII terminal — or a PC running terminal emulation such as the Kermit software included with the AutoMax Programming Executive — can be connected directly to the card for local monitoring and hardware-level fault finding without the full programming suite.

Topology flexibility: The Reliance Electric 57C404C​ supports both the coaxial bus network, using RG-59/U or RG-11/U cable with 75 ohm terminating loads at both ends and passive taps at each drop, and a fiber-optic active star network using stand-alone transceivers and a transceiver hub. Fiber is selected where total electrical isolation and high noise immunity are required, and switching介质 does not affect the protocol, application software or module operation.

Application Field

The Reliance Electric 57C404C​ is found wherever an AutoMax system was installed as the coordinating layer of a long, fast, physically distributed machine. Metals is the classic territory: rolling mills, strip processing lines, annealing and pickling lines and coil handling systems, where several racks must share tension, speed and position references with deterministic timing, and where losing network communication means stopping the line rather than degrading it.

Paper and converting is the second major stronghold. Paper machines, winders, coaters and corrugators use multiple AutoMax racks distributed along a machine that can be hundreds of metres long, and the Reliance Electric 57C404C​ is what keeps section drives, tension loops and auxiliary systems reading the same process image. Material handling and automotive assembly apply the same principle to conveyor networks, transfer lines, paint shops and body shops, where racks are spread across large buildings and the coax or fiber trunk ties them into one coordinated sequence.

In continuous process industries — cement, mining, chemical, rubber, textiles and power auxiliaries — the Reliance Electric 57C404C​ links remote I/O racks back to a central control rack across distances up to 3,000 feet on RG-59/U or 6,000 feet on RG-11/U, and considerably further over fiber.

As a maintenance item, the Reliance Electric 57C404C​ is specified for a recognisable set of situations: a rack that has dropped off the network and shows a fault code on its 7-segment display; intermittent communication traced to a missing or damaged 75 ohm terminating load, a faulty passive tap or a drop cable that has been disturbed; expansion of an existing line by adding another drop; and preventive spares holding for plants that cannot tolerate an open-ended lead time on a discontinued card.