User Manual

Appendix D RS-485 Network 55

D.1 Basic Network Layout

Multi-drop RS-485 implies that there are two main wires in a segment.

The connected systems tap from these two lines with so called drop

cables. Thus all connections are parallel and connecting or disconnect-

ing of a node doesn’t affect the network as a whole. Since ADAM-5000

systems use the RS-485 standard and an ASCII-based commands set,

they can connect and communicate with all ASCII-based computers and

terminals. The basic layouts that can be used for an RS-485 network are:

Daisychain

The last module of a segment is a repeater. It is directly connected to the

main-wires thereby ending the first segment and starting the next seg-

ment. Up to 32 addressable systems can be daisychained . This limitation

is a physical one. When using more systems per segment the IC driver

current rapidly decreases, causing communication errors. In total, the

network can hold up to 256 addressable systems. The limitation on this

number is the two-character hexadecimal address code that can address

256 combinations. The ADAM converter, ADAM repeaters and the host

computer are non addressable units and therefore are not included in

these numbers.

Figure D-1: Daisychaining

Coverter

RS232/RS485

RS-232

RS-485

Repeater

Setgment 2Setgment 1

1 2 N 1