lclarke@questor.wimsey.bc.ca (Lawrence Clarke) (12/31/90)
The Network Administrator's guide tells you how to convert a from the new NeXTstation's RS423 serial port to an RS232 port. But they forgot to mention that the RS423 uses +- 5 volts and an RS232 uses +- 12 volts. I have some equipment that was built to RS232 specs and will not work with the NeXTstation. Some of the newer modem's out there will work though, as most of them were not built to RS232 specs. There's more than just a pinout difference between the 2 standards (RS423 - RS232). USER'S BEWARE !!! /==============================================================\ | lclarke@questor.wimsey.bc.ca | c/o TRIUMF Operations | | larry@triumfcl.bitnet | University of B.C. Canada | | Compuserve: 70441,1776 | 4004 Wesbrook Mall | | Phone: +1 604 275-5902 | Vancouver, British Columbia | | FAX: +1 604 275-4184 | Canada V6T 2A3 | \==============================================================/
lerman@stpstn.UUCP (Ken Lerman) (12/31/90)
In article <qce1u1w163w@questor.wimsey.bc.ca. lclarke@questor.wimsey.bc.ca (Lawrence Clarke) writes:
.The Network Administrator's guide tells you how to convert a from the new
.NeXTstation's RS423 serial port to an RS232 port. But they forgot to
.mention that the RS423 uses +- 5 volts and an RS232 uses +- 12 volts.
.I have some equipment that was built to RS232 specs and will not work with
.the NeXTstation. Some of the newer modem's out there will work though, as
.most of them were not built to RS232 specs. There's more than just a pinout
.difference between the 2 standards (RS423 - RS232).
.
.USER'S BEWARE !!!
.
.
./==============================================================\
.| lclarke@questor.wimsey.bc.ca | c/o TRIUMF Operations |
.| larry@triumfcl.bitnet | University of B.C. Canada |
.| Compuserve: 70441,1776 | 4004 Wesbrook Mall |
.| Phone: +1 604 275-5902 | Vancouver, British Columbia |
.| FAX: +1 604 275-4184 | Canada V6T 2A3 |
.\==============================================================/
My recollection is that RS232 requires the source of a signal to
generate from plus or minus six volts to plus or minus twenty-five
volts. (Plus for a mark and minus for a space, I think.)
The receiver of an RS232 signal must be capable of receiving from plus
three to plus thirty (I think) and from minus three to minus thirty.
Thus, a signal of +-5 volts does not meet RS232 specs, but if it is
connected to a conforming receiver, it should work fine.
Kenslfields@uokmax.ecn.uoknor.edu (Scott L Fields) (01/01/91)
In article <qce1u1w163w@questor.wimsey.bc.ca> lclarke@questor.wimsey.bc.ca (Lawrence Clarke) writes: >The Network Administrator's guide tells you how to convert a from the new >NeXTstation's RS423 serial port to an RS232 port. But they forgot to >mention that the RS423 uses +- 5 volts and an RS232 uses +- 12 volts. >I have some equipment that was built to RS232 specs and will not work with >the NeXTstation. Some of the newer modem's out there will work though, as >most of them were not built to RS232 specs. There's more than just a pinout >difference between the 2 standards (RS423 - RS232). I would think that there would be few devices out there would fail to work on that merit. The usual electronics behind a rs232 interface do not really care whether the input is being driven buy +-5 to +-15 volts. as long as the signal crosses the zerovolt threshold by about 2 volts. The only reason it is 12 volts is so that the cable length can be of that distance (and in practice, usually a lot longer) You will get a significant drop in the line voltage due to resistance and the cable will act like an antennae (if it is not shielded). The increase in voltage is also a noise barrier. But there may be equipment out there that is that finicky. Can't imagine why?
madler@pooh.caltech.edu (Mark Adler) (01/01/91)
Lawrence Clarke (lclarke@questor.wimsey.bc.ca) warns: >> But they forgot to >> mention that the RS423 uses +- 5 volts and an RS232 uses +- 12 volts. >> I have some equipment that was built to RS232 specs and will not work with >> the NeXTstation. If it cannot handle +/-5v, then it is not built to RS-232 specs. The specs allow a transmitter to use anything from +/-5v to +/-25v and require that a receiver respond to signals as low as +/-3v. The two volt difference is to allow for a voltage drop on long cables (in reality, the drop is much less than that). If you are having problems connecting RS-232 to the NeXTstation, blame everything else (wiring, ground loops, modem not on, etc.) before thinking that it is incompatible voltage levels. It may be, but it's quite unlikely. Mark Adler madler@pooh.caltech.edu