HP A4500A - VMEbus Single Board Computer 744 Motherboard Manual page 77

RS-423
The RS-423 standard (also known as CCITT V.10) has a maximum data
transmission rate of 100 kBaud at distances up to 250 feet/80 meters. It can be used
at a maximum distance of 4000 feet/1200 meters at data rates less than or equal to
5 kBaud.
The maximum cable length and data rate are dependent upon the rise time of the
signal carrying the digitial data. A fast rise time allows higher baud rates, whilst a
slow rise time allows for longer cable lengths. The rise time is determined by the
hardware used. It is not usually possible to change it. Consequently, an RS-423
driver can be tuned to support high data rates or long cable lengths, but not both.
RS-423 is a recent standard is not yet as commonly used as RS-232. However, high
baud rates and long distance capabilities are increasing the popularity of the RS-423
electrical standard.
RS-422
Single-ended data transmission is unreliable at very high data rates, over very long
distances, or in noisy environments. For these applications, differential data
transmission can provide superior performance. It can eliminate the effects of
ground shifts and induced noise. On a differential transmission line, ground shifts
and induced noise become common mode noise.
By using differential data transmission, the RS-422 standard (also known as
CCITT V.11) supports data rates of up to 10MBaud at distances equal to, or less
than, 30 feet/10 meters. It supports cable lengths of up to 4000 feet/1200 meters at
data rates up to 100 kBaud.
RS-423 Application
Data
In
RS-422 Application
Data
In
RS-423
Interface
RS-422
Interface
optional R t
A note on standards 8
Data
Out
Data
Out
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