Roland MPU-401 overview
Roland MPU-401 Midi Processing Unit.The Roland MPU-401 MIDI PROCESSING UNIT is designed using a CPU and a custom LSI hand-shake controller for the MIDI bus syst...
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Manufactured byRoland
Product groupAudio Interfaces
DescriptionRoland MPU-401 Midi Processing Unit.The Roland MPU-401 MIDI PROCESSING UNIT is designed using a CPU and a custom LSI hand-shake controller for the MIDI bus system. The MPU-401 connects to a HOST computer via the DATA bus and uses handshaking and interrupts. The MPU-401 may be used as a memory-mapped or I/O mapped device.Roland recognizes the difficulties and weaknesses of using a simple UART or 'DUMB' interface to the MIDI bus and has decided to set out on a program to development this 'intelligent' microprocessor based MIDI interface. This led to the development of a special LSI handshaking controller which drastically reduces the parts count in the interface. Connection to almost any kind of personal computer is now possible due to the simplicity of this hardware interface. The use of interrupts as opposed to polled port techniques greatly adds to the potential of MIDI software applications.
Key FeaturesThe use of an intelligent interface for the MIDI system allows the HOST computer to perform other tasks while the MPU-401 is recording and/or playing. The MPU-401 operates as a 'background' processor using interrupts to the HOST computer to send recorded data to the HOST's memory and requesting data from the HOST to send out on the MIDI OUT port. Because of the above, operations such as disk I/O (if the HOST is using a OMA controller), screen updates, user interface, or any other application functions may be run concurrently while recording or playing MIDI data. The MPU-401 functions as an 8 track MIDI data recorder, looking after all aspects of the recording and playing of musical data, except for HOST memory management. Each track can be polyphonic and multichanneled. The only jobs that the HOST computer must do to look after the MPU-401 are: 1. The sending and receiving of commands to the MPU-401 and; 2. The reading and writing of MIDI data to memory, and organization of memory. The MPU-401 looks after all external SYNC functions, including MIDITIMING CLOCKS ($F8), a Roland DIN SYNC output, an FSK tape sync port (!), and internal timing control. The internal 'TIMEBASE' may be set to one of seven different divisions per beat; 48, 72, 96, 120, 144, 168 or 192. The most commonly used functions are enabled at POWER UP as DEFAULTS, but these default values may be changed on the fly by the HOST. For example, the default TEMPO is 100 beats per minute (BPM), but this may be changed in real time to any tempo within the range of 8 BPM to 250 BPM. Also, the RELATIVE TEMPO and RATE of TEMPO CHANGE (GRADUATION) may be changed in real time, thus allowing the HOST to become the 'CONDUCTOR' of the MPU-401 by automatically changing tempo while recording or playing. The MPU-401 contains 1 RECORD COUNTER; 8 PLAY COUNTERS; 1 CONDUCTOR timer for timing special data; a MIDI IN TABLE which flags each incoming MIDI NOTE ON and clears it upon receiving NOTE OFF or ALL NOTES OFF; 4 CHANNEL REFERENCE TABLES which flag all MIDI NOTE ONs played by the MPU-401 and clears them when sending a NOTE OFF, an ALL NOTES OFF or a STOP PLAY; a 8 PLAY BUFFERS which hold the next MIDI note event to be played in each track; a PROGRAM CHANGE BUFFER which holds the last MIDI PROGRAM CHANGE since the most recent stop; a MIDI Channel filter to allow only selected MIDI channels to pass to the host; a MIDI MESSAGE FILTER for screening out selected MIDI controllers; a UART MODE for applications not requiring the intelligence of the MPU-401; a programmable audio METRONOME which will play any time signature; a synchronization system for MIDI sync, Roland SYNC 24 and FSK (!) type TAPE SYNC; and a full set of intelligent commands which may be used by a HOST application to create any type of MIDI system.
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