Simple MIDI?

Mikko Helin MHELIN at
Wed Jan 21 15:11:08 CET 1998

>Some year ago I posted a schematic of a thing with a 6850 and a couple of
>hex inverters that sent program change status and data. It went to the
>music machine archives at hyperreal but I don't know if it's still there or
>not. The problems is, I haven't seen a 6850 or seen one for sale in a long

No schematics there, just a text file:

Data sheets of MC6850 can not be found at Motorolas www-site,
but they have the MFax system for ordering data sheet (you'll need 
the fax).

Use the page to search for 6402
data sheets. It seems to be still in production. An example of the use of
6402 can be found here:

Other 6402 chips are AY-3-1015 and COM8017, Harris part is CDP6402.

I have a future PC MIDI interface project (when I've got my Telecaster
ready,  built the tube combo amp for it, built an external ADC & DAC
for AudioPCI of CS4222 and built a case for all analog modules and
midi2cv converter) where I'm going to use IDT7402 1 kB FIFOs and
COM8017's (6850's could do as well if they are available) for
multi-port parallel port MIDI interface. I don't like any MIDI
interfaces  that connect to serial port or doesn't have large enough
FIFOs, as they kill the timing when they wait for ready-to-send status
in status polling loooop. So if there's a large FIFO, just a single
"out dx,al" instruction is what is needed, assuming sys-ex data size
doesn't exceed that 1 kB (there are pincompatible 8 kB versions of the
same FIFO's that can be used instead).


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