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User's Guide ADI-648 © RME
10. MIDI
10.1 MIDI Transmission
MADI allows for a transmission of 64 audio channels over long distances with a single line –
perfect. But what about MIDI? Be it remote control commands or sequencer data, in practice
only a single MADI line will not suffice. Therefore the ADI-648 also has a MIDI I/O port. The
data at the MIDI input are being included into the MADI signal invisibly, and can be collected at
the MIDI output of another ADI-648, or a Hammerfall DSP MADI, at the other end of the MADI
line.
Technically every single MADI channel includes several additional bits, containing various in-
formation (Channel Status). RME use the usually unused
User Bit
of channel 56 (channel 28 in
96k Frame mode), to transmit MIDI data invisibly within MADI, ensuring full compatibility.
The block diagram shows the basic
MIDI operation. The MIDI input signal is
added to the MADI output signal. At the
same time it is sent to the 648's main
controller. Its request resonses will be
sent to the MIDI Out only. The MIDI
data present in a MADI input signal will
also show up at the 648's MIDI output.
The MIDI input signal will never be
transferred directly from MADI to MADI,
no matter how the matrix router is set
up.
Note on bigger MADI networks: A MIDI cable connecting MIDI output and MIDI input of the
ADI-648, will realize a direct pass-through of MIDI, from MADI input to MADI output.
10.2 Remote Controlling the ADI-648
Up to firmware 1.4, the MIDI port did serve only for transmission of MIDI data via MADI. Since
firmware 1.5, the unit can be completely remote controlled via MIDI. The CPU shown above
not only bypasses the MIDI data, but also reacts on specific commands.
Furthermore, upon request the CPU will report the compete device status. This includes all
controls and LEDs on the front plate, plus the current MADI input state (56/64-channel mode,
48/96 kHz frame). Each ADI-648 can be programmed with its own ID, providing a separated
remote control of multiple devices via a single MIDI channel. A description of the MIDI imple-
mentation is found in section 15.
To remote control an ADI-648 from a Hammerfall DSP via MADI, MIDI input and MIDI output
have to be connected with a MIDI cable (loopback cabling). As can be seen in the block dia-
gram on the next page, this setup provides a complete data path for MIDI in both directions.
But this method also prevents any other usage than remote controlling the ADI-648. MIDI via
MADI is no longer available for other units. This problem is solved by an external
MIDI Merger
,
mixing multiple MIDI inputs to one output. The unit is placed directly before the MIDI input of
the ADI-648, and will send both the MIDI-Out data of the ADI-648 as well as other unit's MIDI
data to the 648's MIDI input. Accordingly, a
MIDI Splitter
allows to use the 648's MIDI output
with multiple devices, as it sends the output data to multiple outputs at the same time.