Message-ID: <175@qumix.UUCP>
Date: Wed, 7-Nov-84 14:27:11 EST
Article-I.D.: qumix.175
Posted: Wed Nov  7 14:27:11 1984
Date-Received: Thu, 8-Nov-84 08:08:03 EST
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Organization: Qume Corp., San Jose, CA
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Subject: Mac to Commodore printer interface

This is a summary of the request for info on RS422 to IEEE488 that I
posted on the net recently.

1. There was more response than I expected.  The general consensus
seems to be that this requires an extra circuit to handle the timing
but nobody knows what it is.         

2. The Commodore dot matrix printer does not have a standard IEEE488
interface so that is the wrong word to describe it.

3. The timing is tricky.  One response seemed to say that the data is
clocked in on the clock pulses.  Does anyone know the duty cycle of
the clock (on/off time)?  Also, is it clocked by edges or when the
level is low or high.  If I knew this, I might be able to cludge up a
555 timer circuit to generate the clock asyncronously.  Just getting it
to print at all would be a major step forward.

Message-ID: <290@sdchema.UUCP>
Date: Mon, 12-Nov-84 16:35:30 EST
Article-I.D.: sdchema.290
Posted: Mon Nov 12 16:35:30 1984
Date-Received: Wed, 14-Nov-84 04:32:59 EST
References: <175@qumix.UUCP>
Reply-To: jmw@sdchema.UUCP (John M. Wright)
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Xref: sdcsvax net.micro:8338 net.micro.cbm:883
Summary: 

I think it will be more trouble than it's worth to try to
interface a non-CBM machine to your CBM printer.  See if you
can find a copy of the July '83 issue of COMPUTE!;  an article
by Jim Butterfield,  "How the VIC/64 Serial Bus Works", will
let you know something about what you are up against (but not
enough to actually solve the problem;  the only sufficiently
detailed info I have seen on how the serial bus and devices
interact comes from a dissasembly of the actual routines that
drive the bus.)

Why go that way, anyway?  I guess you somehow happen to have the
CBM printer on hand?  I haven't actually used one myself, but they
seem to be widely held to be pretty poor.  I find it pretty compelling
that there are *dozens* of interfaces available for driving standard
(either RS-232 serial, or parallel)  printers from a VIC or 64,
but I have never seen one for driving a CBM printer from a "standard"
port.

I think I saw that you had interfaced a VICMODEM to a standard
RS-232 port;  that was probably relatively straightforward because
the VICMODEM interfaces with the 64 not through its "serial bus",
but through what is intended to be and RS-232 connection (at least,
that's what Commodore calls it) (except for voltage levels!).

Good luck, anyway.

John Wright