PCMCIA 1 Port RS422/485
Additional 422/485 Operation
Chapter 4 Page 35
CHAPTER 4
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
D
R
T T L
T T L
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 than one device may transmit data, the RTS line is used as
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