Xref: utzoo rec.music.synth:17084 comp.sys.ibm.pc.hardware:3084 sci.electronics:15611 Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!philpav!rzi From: rzi@philpav.tds.philips.se (Roman Zielinski) Newsgroups: rec.music.synth,comp.sys.ibm.pc.hardware,sci.electronics Subject: Re: MIDI Summary: why MPU401 Message-ID: <505@philpav.tds.philips.se> Date: 14 Nov 90 09:31:57 GMT References: <4840.tnews@basso.actrix.co.nz> Organization: Philips TDS, Stockholm, Sweden Lines: 45 In article <4840.tnews@basso.actrix.co.nz>, dgold@basso.actrix.co.nz (Dale Gold) writes: > Quoted from - cs161fhn@sdcc10.ucsd.edu (Dennis Lou): > > [...] > > Why can't you do this on an IBM? What does the Roland MPU-401 > > have that a modified serial interface doesn't? > > [...] A simplest MIDI-interface can be built as an UART plus opto-isolator working in 31kb/s speed. Normal UARTs in PCs can work up to 19.2kb/s (You can force them to higher speeds, but.... what happens if your CPU will be too busy to handle all interrupts from UART?) MPU401 is a Motorola 6800-based system (not just an UART shifting out/in data to/from the line). It is very clever card performing all timing work. It also keeps track on measures, tempos, metronome bit, etc MPU and application use a handshaking protocol so you can transfer data and events in both directions simultanously. For example, from application you send events tagged with time-to-next event, like: time-to-next-event 05 ch=1 tone-on tone velocity 25 ch=2 tone-on tone velocity 36 ch=5 program-change prog 55 ch=1 tone-off tone measure measure 01 ch=2 tone-off tone Due the timing facilities the application can work quite asyncronously to the hardware, and it cannot be done with a pure UART system. Roland has a techn spec for $5-10, it is about 70-80 pages... +-------------------------------------------+ _--~--_ | Roman M. Zielinski | ---- / \ ---- | Philips Tele & Data System AB | ---- ( |^^^| ) ---- | S-115 84 Stockholm, Sweden | ---- \ \ / / --- | tel +46 8 782 1373 | |=====| +-------------------------------------------+ |=====| | NET ADDR: rzi@pav.tds.philips.se | |=====| +-------------------------------------------+ ~~U~~