ADLINK NuDAM-65xx Communication Module Networking and Configuration Guide

ADLINK NuDAM Series RS-485 Communication Module Networking and Configuration Practice

In industrial sites, remote and reliable communication between sensors, actuators, and controllers is the cornerstone of automation systems. The RS-485 bus, with its differential transmission, multi station capability, and communication distance of up to 4000 feet, has become the preferred physical layer for distributed data acquisition. The ADLINK NuDAM series not only offers a wide range of I/O modules, but also comes with a complete set of communication infrastructure components, including the RS-232 to RS-485 converter (ND-6520), RS-485 repeater (ND-6510), USB to RS-485 converter (ND-6530), and addressable RS-485 to RS-232 converter (ND-6521). This article will systematically explain how to build a stable and scalable NuDAM RS-485 multi station network from network architecture design, device selection, initialization configuration, command system to troubleshooting, to assist engineers in quickly completing on-site communication deployment.

RS-485 Network Fundamentals and NuDAM Topology

RS-485 adopts differential balanced transmission, supports half duplex or full duplex, and can hang up to 32 nodes under standard driving capability. The NuDAM module, designed with high input impedance, allows up to 128 modules to be connected on the same bus (without the use of repeaters). If combined with repeaters, it can theoretically be extended to 256 nodes (limited by address coding). The NuDAM system adopts a two-wire half duplex RS-485 (DATA+and DATA -) system, with all modules connected in parallel on the same pair of twisted pair cables, forming a multi station network.

The network topology supports simple daisy chain (Figure 1-1), branch topology (Figure 1-2), and free topology (Figure 1-3). In actual deployment, it is recommended to use a daisy chain or a hybrid structure with short branches to avoid reflections caused by excessively long, terminal less branches. Terminal resistors (120 Ω± 2%) must be installed at the end of each physical segment to match the characteristic impedance and eliminate signal reflections. Shielded twisted pair cables should be grounded at one end (usually on the host side) and connected to the protective ground multiple times along the bus to improve anti-interference capability.

Function and selection of core communication module

1. ND-6520 RS-232 to RS-422/485 converter

ND-6520 is a portal device for building NuDAM networks, which converts the host's standard RS-232 serial port into RS-485 signals. The default configuration is 9600 bps, 8 data bits, 1 stop bit, and no checksum (10 bit packet). Built in automatic direction control, no RTS hardware handshake required. Its DB-9 female socket is connected to the host, and the wiring terminals provide DATA+/DATA - (RS-485) and independent TX+/TX -/RX+/RX - (for full duplex RS-422). Supports up to 115.2K baud rate (firmware A1.2 or above), with 2500Vrms isolation and surge protection. Suitable for all hosts with RS-232 port (PC, IPC, laptop).

2. ND-6510 RS-422/485 repeater

When the number of network nodes exceeds 128 or the bus length exceeds 4000 feet, ND-6510 must be inserted to regenerate the signal and extend the communication distance. It provides bidirectional relay function, automatically identifies transmission direction, and does not require programming. Its wiring terminals include two sets of RS-485 (DATA+/DATA -) and two sets of RS-422 (TX/RX pairs), which can flexibly connect different segments. It also supports baud rates of 1200~115.2K with a power consumption of 0.9W. The repeater can be cascaded, but adding one level will increase the delay. In practical applications, it is recommended to have at most two levels.

3. ND-6530 USB to RS-232/422/485 converter

In response to the common lack of RS-232 port in modern computers, ND-6530 provides USB interface to convert multiple serial protocols. It complies with the USB 1.1 specification, plug and play, and supports Windows 98/2000 drivers. The RS-232, RS-422, or RS-485 modes can be switched through the DIP switch on the body. RS-485 supports automatic flow control; RS-232 provides RTS/CTS hardware flow control. It is powered by USB bus (no external power supply required) and has an isolation voltage of 2500Vrms. Specially suitable for expanding serial communication through USB ports on laptops or industrial computers.

4. ND-6521 addressable RS-485/422 to RS-232 converter

ND-6521 is an enhanced version of ND-6520, which is an RS-485 slave device with independent addresses (01~FF). It can route data on the RS-485 bus to sub devices connected to its RS-232 port, such as serial printers, barcode scanners, PLC programming ports, etc. It supports two working modes:

Address mode (default): The host sends a command containing a specific address, which is recognized by ND-6521 and forwarded to the RS-232 device, and the response from the sub device is sent back to the host.

Non Address Mode (Transparent Mode): When enabled through the "Open Data Gate" command (&Addr810), ND-6521 acts as a transparent converter similar to ND-6520, ignoring addresses and directly transmitting all data transparently, suitable for point-to-point communication.