Re: MIDI interfaces

From: Rainer Buchty (
Date: 2002-09-12 12:39:03

> What were the address maps of the popular C64 MIDI interfaces?

As far as I recall there were 3 standards, Siel/JMS, Passport and
Sequential. At least in Germany the first one was standard; all DIY
solutions as published in the 64'er Magazine, its special issues, in the
Keyboard magazine etc. to it. Also the IIRC most common interface sold
over here, the C-Lab interface and their Supertrack & Scoretrack modules,
followed the Siel/JMS standard.

> There seem to have been a few of them, all slightly different. I think
> the strange mapping of the Sound Expander cartridge thru port is
> intended to make the MIDI cartridges appear the same. Any info on C64
> MIDI standards would be gratefully appreciated.

The differences are (citing

                                 Siel/JMS      Passport     Sequential
 Control Register Address          DE04          DE08          DE00
 Transmit Data Register Address    DE05          DE09          DE01
 Status Register Address           DE06          DE08          DE02
 Receive Data Register Address     DE07          DE09          DE03
 Master Chip Reset Command          03            03            03
 Enable Xmit/Rcv Command            16            15            15
 Enable Xmit/Rcv + Rcv Interrupt    96            95            95
 Enable Xmit/Rcv + Xmit Interrupt   36            35            35
 Enable Xmit/Rcv + Both Interrupts  B6            B5            B5

Looks like Passport & Sequential used a 500kHz crystal (-> MIDI rate =
counter/16) rather than 2MHz (-> MIDI rate=counter/64) as the Siel/JMS
variant did.



Rainer Buchty, LRR, Technical University of Munich @ Garching
Phone: +49 89 289-18477, Fax +49 89 289-17662, Room 01.06.061

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