irwin@uiucdcs.UUCP (irwin ) (04/04/84)
#R:uicsg:7600018:uiucdcs:10400123:000:563 uiucdcs!irwin Apr 3 12:33:00 1984 The RS-232 transmit and receive signals are referenced to ground, the RS-432 signals are not. They are a balanced pair driven by a differential driver and received by a differential receiver chip. There have been articles in BYTE showing how to make an adaptor to convert from one to the other. The idea is that the RS-432 is less prone to noise since one wire is driven negative while the other is driven positive in the pair for each logic level change. A foreign "glitch" induced into the pair would drive them both the same direction and it would be ignored.
irwin@uiucdcs.UUCP (irwin ) (04/04/84)
#R:uicsg:7600018:uiucdcs:10400124:000:222 uiucdcs!irwin Apr 4 01:36:00 1984 Opps, I goofed on that one, what I thought I read was RS-422. I am not familiar with the RS-432 signals. The RS-422 is as I stated in the previous response, I will look around and see what I can find on the RS-432 set-up.
sct@lanl-a.UUCP (04/09/84)
RS-423 however. This EIA specification is for data generators and receivers only (just as RS 422 is) and should not be construed as a replacement for RS-232. In fact RS 423 generated signals can work with RS-232 interfaces. The EIA spec for RS-449 is the valid spec for comparison with RS-232. It provides for the use of either RS-422 (balanced transmission) or RS-423 (unbalanced transmission). The maximum data rates with RS-423 are similar to those of RS-232 interfaces while the maximum data rates with RS-422 are about 1 Mbit/s (depending on distance).
dmt@hocsl.UUCP (04/10/84)
It is my understanding that the "new" standards (RS-422, -423,
& -449) have separated the functional specifications from
the electrical. The "old" RS-232 had both functional and electrical.
Let's try a picture, and hope my facts are right:
----OLD---- ----------------NEW---------------------------
RS-232 RS-422 RS-423 RS-449
FUNCTIONAL 25 leads - - 37 leads
ELECTRICAL Unbalanced to Balanced to Unbalanced to -
20 Kbps ~1Mbps >20 Kbps
Thus, a 25-pin subset of RS-449 with drivers meeting RS-423 would be
compatible with RS-232.
Dave Tutelman
AT&T IS - Holmdel
...!hogpc!hocsf!hocsl!dmtgurr@west44.UUCP (04/11/84)
<>
The main difference between RS232 and RS432 is that (as everyone knows) the
RS232 signals use +12 and -12 volts, whereas RS432 uses +5 and 0V. There is
not a great deal of problem in interfacing the two (at least, I have found
none) mainly since +5 is high enough to be recognised by the RS232 receiver
as +12 and also that the signal is usually pulled down to -12V by the
receiver (at least on large machines). If you do have problems interfacing
the two, try dragging the signal down to -12V by a suitable resistor (eg
1K).
cbosgd
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Dave Gurr, Westfield College, Univ. of London, England.