Charli@cup.portal.com (01/24/88)
I have an IBM clone and a Commodore 128. I like to download on BBS's using my IBM, but I would like to be able to download some programs for the Commodore and then transfer them directly, without hooking up both modems and doing it by phone. Can anyone tell me how to hook up the two machines so that I can do this? Charli
Brendan@cup.portal.com (02/13/88)
You may want to buy a 'null modem', which acts in place of the phone company
and phone lines between the computers...also, I think I saw something in one
of the old Transactor magaziines..I only have sketchy knowledge about the null
modem, and I'm sure there are others out there who could elaborate...
Brendan Kehoe
UUCP: ...sun!portal!cup.portal.com!Brendan_Patrick_Kehoeberger@clio.las.uiuc.edu (02/16/88)
There are many ways to make a null modem cable, but here's one that
should work for most applications. I assume you have standard RS-232
25 pin D-type connectors on both ends. Otherwise you'll have to
translate the wire list for your own connectors.
1 - 1
2 - 3
3 - 2
4 - 5
5 - 4
6,8 - 20
7 - 7
20 - 6,8
Basically, this crosses data transmit and receive, CTS/RTS,
DSR/DTR, and gives you a carrier detect indication as well.
Mike Berger
Department of Statistics
Science, Technology, and Society
University of Illinois
berger@clio.las.uiuc.edu
{ihnp4 | convex | pur-ee}!uiucuxc!clio!bergerbilbo@pnet02.cts.com (Bill Daggett) (02/16/88)
A null modem I believe is in reference to a direct cable hook-up between two
computers and that physically there is no modem. The null modem cable carries
the same essential data lines that a RS232 cable carries from your computer to
the modem with the same pinout but one important exception: To work as a
"null" modem cable the send and receive wires are crossed. In other words,
send and receive data at one plug goes to the receive and send data
respectively at the other plug. From what I hear you can tie just about any
two computers together this way.
BTW, when I was transfering some old Apple files to the Amiga I experienced
great difficulty too and not with getting the computers to talk to each other
but in the file data format. There was a hi bit / lo bit problem with the
Apple. It seems that Apple DOS 3.3 set the hi bit or didn't - I don't
remember which and that ProDOS did the opposite. I would send the file to the
Amiga and when I took a look at it it would be total garbage - the alternate
character set. I transfered the files on the Apple from DOS 3.3 to ProDOS or
vic versa - you get the idea? And sent the file again to the Amiga and
hooray! It was readable.
Bill
UUCP: {ihnp4!scgvaxd!cadovax rutgers!marque}!gryphon!pnet02!bilbo
INET: bilbo@pnet02.cts.compeiffer@umn-cs.cs.umn.edu (Tim J. Peiffer) (02/16/88)
In article <3154@cup.portal.com>, Brendan@cup.portal.com writes: > You may want to buy a 'null modem', which acts in place of the phone company > and phone lines between the computers...also, I think I saw something in one > of the old Transactor magaziines..I only have sketchy knowledge about the null > modem, and I'm sure there are others out there who could elaborate... > UUCP: ...sun!portal!cup.portal.com!Brendan_Patrick_Kehoe You are correct in assuming that what is a null modem. Your local Radio Shack stocks one that cost's approximately $20.00. If you do not want to pay through the nose, you can hook up one as the following 1 chassis gnd <-> chassis gnd 1 2 txd <-> rxd 3 3 rxd <-> txd 2 4 rts <-> cts 5 5 cts <-> rts 4 7 sig gnd <-> sig gnd 7 6 & 8 (dsr & dcd) <-> dtr 20 20 dtr <-> (dsr & dcd) 6 & 8 All other connections are unnecessary for most RS-232 application standards. Just remember that the big three are txd,rxd, & sig gnd. This should hold for just about every application that you need. Commodore does not implement RS-232 very well. What they implement is the method of control, not the voltage level; most certainly not the pin-outs. RS-232 voltages range from -25vdc (or -15) to +25vdc (or +15). Commodore chose to leave out the required line drivers and receivers. Their voltage levels range from 0vdc to +5vdc. You may elect to get around this problem by purchasing the required converter from JameCo Electronics. The unit retails for approximately $39.95. I have used this method to do direct machine to machine transfers up to 19200 Baud. It is reliable in the area of data, but handshake can become a little shakey (pardon the pun). Tim Peiffer Computer Science Systems Group Computer Science Department University of Minnesota, Minneapolis, MN 55455. (Ding-aling Net 612-625-0876) peiffer@umn-cs.cs.umn.edu peiffer@umn-cs.UUCP
blume@netmbx.UUCP (Heiko Blume) (02/21/88)
i think a explicit 7 bit text transfer with kermit should *not* transfer
the highest bit !? that might solve the problem easily.
{i didnt try yet, but i had the same problem once, all inverse chars :-}
--
Heiko Blume # DOMAIN: blume@netmbx.UUCP { BITNET: ( mixed }
Seekorso 29 # BANG : ..!{backbone}!netmbx!blume
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Telex : 183008 intro d # Fax : (+49 30) 882 50 65 terry@wsccs.UUCP (terry) (02/28/88)
In article <18600039@clio>, berger@clio.las.uiuc.edu writes: > > There are many ways to make a null modem cable, but here's one that > should work for most applications. I assume you have standard RS-232 > 25 pin D-type connectors on both ends. Otherwise you'll have to > translate the wire list for your own connectors. > > 1 - 1 > 2 - 3 > 3 - 2 > 4 - 5 > 5 - 4 > 6,8 - 20 > 7 - 7 > 20 - 6,8 Unfortunately, this neglects the fact that a number of modems do not assert CTS unless they have DCD. The above cable is fine for incoming calls but lousy for outgoing. Here is a more reliable cable: 1 ---- /* connect pin one only on CPU side to avoid ground loops*/ 2 ---- 3 3 ---- 2 4 \ / 4 /* Forcing the self-satifaction at the cable end avoids wires, 5 / \ 5 but you may need to wire it thru if the modem requires CTS 6 -. but does not assert RTS until carrier, like Multitek.*/ 8 -+--20 .- 6 /* If your call-out software opens the port right, it should 20--+- 8 not need DCD prior to talking to/reading from the port*/ 7 ---- 7 The same cable should work from machine to machine (DTE-DTE, DCE-DCE) and and from DCE machine to a modem, or DTE machine to a terminal, if the terminal asserts DTR (DCD for terminals). A good book on this is titled 'THE RS-232 SOLOUTION'. My cable comes from supporting terminal emulation/file transfer software on UNIX boxes 9-6 5 days a week, and from participating in writing said software. Note that the same reservations apply on translation of this cable to 9-pin, 15-pin, or NCR boxes (you CAN'T call out ttya or ttyb on an NCR box. ttyb is the console, and ttya is the call-in-only maintenance port). If you are talking about an expander board for a UNIX or Xenix on an AT clone, it depends on the board. | Terry Lambert UUCP: ...!decvax!utah-cs!century!terry | | @ Century Software or : ...utah-cs!uplherc!sp7040!obie!wsccs!terry | | SLC, Utah | | These opinions are not my companies, but if you find them | | useful, send a $20.00 donation to Brisbane Australia... | | 'There are monkey boys in the facility. Do not be alarmed; you are secure' |