Date : Sat, 09 Jul 1988 22:03:22 GMT
From : necntc!ima!cfisun!lakart!dg@husc6.harvard.edu (David Goodenough)
Subject: Kaypro and Spinwriter 7710
From article <12412216898.11.D-ROGERS@EDWARDS-2060.ARPA>, by D-ROGERS@EDWARDS-2060.ARPA:
> I received no reply on this before and i still need help. I have a friend
> with a Kaypro 4 and an NEC 7710 Spinwriter. They don't seem to talk to
> each other. I've tried simple things like PIPing a text file to various
> ports, e.g. LST:, PRN:, PUN:, AUX: in every case the system hangs, as
> though waiting for a DTR. The printer self tests OK and both units are set
> to run at 1200 baud, 8 bits, no parity. I don't even get garbage. The NEC
> has a DB25 connector; that with the baud and parity switches makes me
believe it
> uses a serial interface. Is there something else i need to know to get
> the Kaypro to dump a character stream? It also has a parallel port, but
> the software didn't have any procedures to reassign any logical devices.
> H E L P !
> [dale]
> -------
I'm no Kaypro Guru, but reading between the lines from above I interpret it
to mean that your friend's Kaypro has a serial port for a modem and a parallel
port for a centronix style printer. The problem with the "DB25" RS232
connectors is that there are two ways of wiring them: DTE (Data terminal
equipment) and DCE (Data carrier equipment). DCE refers to modems, which
transmit data on pin 3, DSR (Data Set Ready) on pin 6, DCD (Data carrier
detect) on pin 8 and CTS (Clear to send) on pin 5. DTE refers to just about
everything else: terminals, the PUN: RDR: port on the back of a Kaypro, and
printers: these devices transmit data on pin 2, DTR (Data terminal ready)
on pin 20, and RTS (Request to send) on pin 4. Now if you've been following
all the above, you will have noticed that BOTH the printer AND the Kaypro
are transmitting on the same pins (2,4,20) and listening to the same
pins (3,5,6,8). What you need to do is to make up a crossover cable
(sometimes called a null modem) which does the following: on both ends
pin 2 at one end goes to pin 3 at the other end, pin 20 at one end
goes to pins 6 and 8 at the other, and pin 4 at one end goes to pin
5 at the same end:
2------------\/-----------2
3------------/\-----------3
4---+ +---4
5---+ +---5
6-----+ +-------6
8-----+-----\/----+-------8
20----------/\-----------20
with pin 7 (ground) wired straight through. What this does is to trick
each end into thinking the other end is a modem, and everyone is happy.
I can't guarantee that this is the solution, but if you've been using
the same cable to talk to the printer as you talk to a modem with then
I'll take even's money bets that's why it wasn't working.
--
dg@lakart.UUCP - David Goodenough +---+
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