MMB 2x2
MIDI Merge Box
Model 8-252 ver. 1.2
Copyright © 2009 CHD Elektroservis
All rights reserved. No part of this publication may be reproduced in any form without the written permission of CHD Elektroservis, s.r.o.
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1. INTRODUCTION
MMB 2x2 is device that merges MIDI data from four MIDI transceivers. Algorithm of internal
operating system and size of data buffers are chosen so that while merging data, all regulations “MIDI
Specification" given by MMA (MIDI Manufacturers Association) are adhered and that device can
process commands and messages of all MIDI standards.
During data merging, priority of different data types is taken into consideration, duplicate data
and all disallowed data (e.g. undefined state bytes, data bytes without state byte, etc.) is eliminated.
Operating system of MMB 2x2 fully respects communication regime „Running Status" – duplicate state
bytes are omitted from MIDI messages and conversely, state bytes are inserted to MIDI messages on
required positions. All above stated operations are carried out by MMB 2x2 automatically, interference
of attendance is not needed.
For increasing the utility value, device is complemented by user adjustable filters of MIDI data
and "Panic" function is also implemented.
1.1. CONTROLLERS AND INDICATORS, CONNECTORS
Pic. 1 – Panels of device
All sockets are on rear panel of the
device. LED indicators (diodes) and manual
controllers are on front panel of the device.
Placement and titles of all components are
shown on pic. 1.
1. System parameters selector
2. Indicator of overflowing of buffers
3. Data on bus A indikcator
4. Data on bus B indikcator
5. Power indicator
6. PANIC button
7. Socket for supply adapter
8. MIDI data input A
9. MIDI data output A
10. MIDI data input B
11. MIDI data output B
1.2. DEVICE FUNCTION
The device processes MIDI data in two identical and independent ways A and B. Signals from
MIDI buses coming to inputs MIDI-IN-A [8] and MIDI-IN-B [10] are galvanicaly insulated by
optocouplers and brought to input filters of MIDI data. Real time data with highest priority are
separated and then they are coming to outputs of signal ways directly if their filtration isn’t requested.
This guarantees minimal delay of MIDI synchronization data. Other data are stored in input caching
buffers and from here data are continuously drawn and merged with data from the other way. Resulting
data are filtered (if output filters are enabled) and stored in output data caching buffers. From there,
data are gradually sent to outputs MIDI-OUT-A [9] and MIDI-OUT-B [11].
Function block diagram of MMB 2x2 is shown on pic.2.
Summary of Contents for 8-252
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