Chapter 5 Additional Rs422/485 Operation; The Rs422 Standard; The Rs485 Standard - Brainboxes CC-357 User Manual

PCI VelocityRS232/422/485 Additional RS422/485 Operation
Chapter 5
ADDITIONAL RS422/485
OPERATION

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

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 resistor
should be used to terminate either end of the main line. If more
Chapter 5 Page 70