Chapter 4; The Rs422 Standard; The Rs485 Standard - Brainboxes CC-310 Hardware Manual

RS422/485 Information
ADDITIONAL RS422/485

The RS422 Standard.

The RS422 standard defines a serial communications
standard. RS422 is a high speed and/or long distance data
transmission. Each signal is carried by a pair of wires and is thus a
differential data transmission system. Over distances up to 40 feet
the maximum data rate is 10 Megabits per second, and for distances
up to 4000 feet the maximum data rate is 100 Kilobytes per second.
A 120-Ohm resistor should be used to terminate the receiving end
of the line. It is generally used between one transmitter receiver pair
to ONLY one other transmitter receiver pair, but each output can
drive up to 10 receivers.

The RS485 Standard.

The RS485 standard is similar to the RS422 standard upon
which it is based. The main difference is that up to 32 transmitter
receiver pairs may be present on the line at one time. A 120-Ohm
Chapter 4 Page 40
PCI VELOCITY / OPTO ISO RS422/485

Chapter 4

OPERATION
RS422 Standard
1 Driver up to 10 Receivers
Line Length
40 Feet = 12m
400 Feet = 122m
4000 Feet = 1219m
Max Data Rate
10 Mbits/sec
1 Mbits/sec
100 Kbits/sec