len@qumix.UUCP (Leonard Labar) (11/07/84)
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.
jmw@sdchema.UUCP (John M. Wright) (11/13/84)
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