DSEAH@WPI.BITNET (04/20/88)
While scrounging for information to construct a modem cable for my GS, I flipped to the back of some standard Apple documentation only to see a bunch of + and - signs in front of weird names for the pinout. Can somebody tell me what they are in standard RS232 lingo? +--------------------------------------------------------------------------+ | Dave Seah --- Worcester Polytechnic Institute | +-----------------------------------------------+--------------------------+ | Bitnet: DSeah@WPI.Bitnet | We can't receive files! | | Internet: DSeah%WPI.Bitnet@CUNYVM.CUNY.EDU | EMAIL only! | +-----------------------------------------------+--------------------------+
ralphw@IUS3.IUS.CS.CMU.EDU (Ralph Hyre) (04/21/88)
GS serial pinout should be the same as the Mac.
I believe the RXD- and TXD- are connectors are more-or-less RS232
RXD and TXD signals.
- Ralph
--
- Ralph W. Hyre, Jr.
Internet: ralphw@ius2.cs.cmu.edu Phone:(412)268-{2847,3275} CMU-{BUGS,DARK}
Amateur Packet Radio: N3FGW@W2XO, or c/o W3VC, CMU Radio Club, Pittsburgh, PAdouglas@reed.UUCP (P Douglas Reeder) (04/22/88)
STANDARD RS-232 (which no one seems to follow) calls for balanced pair
transmission (data pulses are sent out as positive pulses on the + lines
and negative on the - lines). The signal is recieved with a differential
amplifier. This improves transmission quality as any noise imposed is
imposed on both lines and ignored by the differential amplifier.
This setup is neccesary when you run cables on the order of 100m. Since
microcomputer cables are seldom more than a few feet, everyone cheats on
the standard and there's seldom a problem.
If you need transmission over longer distances than 232 can do, there are
other standards with different rquirements.
--
Doug Reeder USENET: ...!tektronix!reed!douglas
10 Cyclopedia Square from BITNET: douglas@reed.UUCP
Terminus City from ARPA: tektronix!reed!douglas@berkley
Terminus,The Foundation Box 502 Reed College,Portland,OR 97202rrt@halley.UUCP (Robert Teisberg) (04/23/88)
In article <8945@reed.UUCP> douglas@reed.UUCP (P Douglas Reeder) writes: >STANDARD RS-232 (which no one seems to follow) calls for balanced pair >transmission (data pulses are sent out as positive pulses on the + lines >and negative on the - lines). I think you're describing RS-422 here. RS-232 is an unbalanced transmission protocol. If you look at the RS-232 pinouts, you will see that pin 7 is called Signal Ground (SG). This is the return pin for ALL signals in both directions. Because it is unbalanced, RS-232 is limited to short cable runs at low speeds and is vulnerable to noise. >-- >Doug Reeder USENET: ...!tektronix!reed!douglas >10 Cyclopedia Square from BITNET: douglas@reed.UUCP >Terminus City from ARPA: tektronix!reed!douglas@berkley >Terminus,The Foundation Box 502 Reed College,Portland,OR 97202 Bob Teisberg @ Tandem Computers, Inc. ...!ut-sally!im4u!halley!rrt
kamath@reed.UUCP (Sean Kamath) (04/24/88)
In article <8945@reed.UUCP> douglas@reed.UUCP (P Douglas Reeder) writes: >STANDARD RS-232 (which no one seems to follow) calls for balanced pair >transmission (data pulses are sent out as positive pulses on the + lines >and negative on the - lines). The signal is recieved with a differential >amplifier. > [one line deleted. I thought I could get rid of more, but. . .] >This setup is neccesary when you run cables on the order of 100m. Since >microcomputer cables are seldom more than a few feet, everyone cheats on >the standard and there's seldom a problem. > If you need transmission over longer distances than 232 can do, there are >other standards with different rquirements. > >-- >Doug Reeder USENET: ...!tektronix!reed!douglas >10 Cyclopedia Square from BITNET: douglas@reed.UUCP >Terminus City from ARPA: tektronix!reed!douglas@berkley >Terminus,The Foundation Box 502 Reed College,Portland,OR 97202 A very nice discription of rs-422, Doug! *not* rs-232. RS-232 is *level* sensitive. I.e. between 2.5 and 15 volts is "true" (I think. I don't have my handy book here. . .), and from -2.5 to -15 V is a "false". It dies off much faster than rs-422. Most micros use +/- 5V, and so they go about 100 ft. Or less. between 2.5 and -2.5, it's undefined. Realy! Though almost all UARTs, and hence most serial communications devices, below ~1.2V is "False". A *REALLY* good book to get about rs-232 and 422, as well as serial programming with UARTs and stuff (it's written in C, but the first part is a "history" or serial communications) is: _A Programmer GUide to Serial Communications_ by someone. It from Howard Sams, and costs about $24, just like all computer books. Get it at B.Dalton's software etc. I suspect, Doug, that you have been tainted by all the Macs here at Reed :-) Sean Kamath -- UUCP: {decvax allegra ucbcad ucbvax hplabs ihnp4}!tektronix!reed!kamath CSNET: reed!kamath@Tektronix.CSNET || BITNET: reed!kamath@PSUVAX1.BITNET ARPA: reed!kamath@psuvax1.arpa US Snail: 3934 SE Boise, Portland, OR 97202 (I hate 4 line .sigs!)