From: Rainer Buchty (buchty_at_cs.tum.edu)
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
http://www.funet.fi/pub/cbm/documents/projects/other/C64MIDI-INTERFACE.TXT)
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
--
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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