[Octet Design Corporation]

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UM1 universal MIDI interface

preliminary data sheet 7/11/96

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Table of Contents

Description
Specifications
Pin Descriptions
MIDI commands
Ordering Information

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Description

The UM1 is a general purpose interface which uses the MIDI protocol and
cables to communicate with a computer. It provides a convenient hardware
extension to a computer, through its compatible MIDI ports. Its128 I/O ports
can be configured as 128 outputs, or 128 inputs or 64 inputs and 64 outputs.
The inputs/outputs can accomodate various voltages from 5 volt to 40 volts.
The model UM1-P has higher rated outputs (see output specifications).

The MIDI IN port receives commands, the MIDI OUTÊport sends key up and down
messages if the UM1 is setup as an input or partial input mode. The MIDI
OUTÊport also serves as the traditional MIDI THRU port, as it repeats all
signals coming in. For software configuration (using Windows utility
provided), both MIDI IN and OUT must be connected to the computer. However,
it is possible to configure the UM1 without using the software, with the
configuration mode switch. Only the MIDI IN port is required to use the UM1
as an output device, only the MIDI OUT port is required to use the UM1 as an
input device; however, the use of both ports and the software utility adds
some diagnostic features.

The note number (0-127) in the MIDI note messages corresponds to the I/O
port number; with the software utility, the ranges assigned to each 64 I/O
partition can be transposed. A rotary switch selects the MIDI channel (1 to
16). One MIDI port can control up to 16 UM1's, each usually assigned a
different channel. Normal MIDI devices are limited to about 3 in a chain,
but the UM1's fast opto isolator allows 16 units in a chain. If other MIDI
devices are placed on the same port, they will limit the total number of
devices on that port.

Connections:
One one side of the package, 2 standard 5-pin DIN MIDI connectors, the
channel selector switch and the mode selector switch.
On the other side, 4 40-pin headers which include the 128 I/O ports, vibrato
output, PWM outputs, power and ground.

A Windows (3.1 / 95) software utility allows control of all parameters
(channel assignments, mapping, modes, debouncing, etc...), loading of
firmware upgrades. Its diagnostics capabilities include detecting which
outputs are loaded and whether outputs are shorted.
The MIDI compatibility allows the UM1 to communicate with standard MIDI
keyboards and sequencer software.

Applications of the UM1:
¥ organ upgrades
¥ light control
¥ console MIDI encoder (generates MIDI codes from key presses)
¥ MIDI decoder-driver (activates outputs according to MIDI codes received)
¥ Experimental controller
¥ Board Testers
¥ Security System I/O
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Specifications

Parameter                 Min.   Max.   Units
Storage temperature       -40    100    °C
Operating temperature     0      50     °C
Humidity (non-condensing) 0      95     %

Power supply
The power for the UM1's internal circuits is provided at the 40-pin headers.
The same power input is used for the programmable pullup resistors;
usually it is also the power supply of the user's external circuits.
(ie 5 volts for a TTL interface, more for solenoid drive).
Parameter               Min.    Max.    Units    Notes
Supply voltage          4.5     40      Volts
Supply current                  0.4     Amp      no load

Driver Outputs
The 128 open collector driver outputs are provided at the 40-pin headers.
(The output drives low for a key on command).
Active clamps enable driving solenoids or relays directly.
Parameter               Typ.    Max.    Units    Notes
On output voltage       0.2     0.3     Volts    at 50mA load
On output voltage       0.5     0.6     Volts    at 100mA load
On output voltage       1.3     2.0     Volts    at 250mA load
Switching time          200             nsec
duty cycle                      100     %        all outputs at 120mA load
duty cycle                      30      %        all outputs at 250mA load

UM1-P On output voltage 0.1     0.2     Volts    at 100mA load
UM1-P On output voltage 0.3     0.5     Volts    at 250mA load
UM1-P On output voltage 0.7     1.0     Volts    at 500mA load
UM1-P duty cycle                100     %        all outputs at 250mA load
UM1-P duty cycle                40      %        all outputs at 500mA load

Inputs
The 128 inputs are provided at the 40-pin headers.
Normally active low with 10 kohm pull-up resistors, they can be configured
as active high with 10 kohm pull-down resistors. Additional pull-up/down resistors can be added externally.
They have a programmable debounce time, so the UM1 can be used as a console encoder.
Parameter                  Min.    Max.    Units    Notes
Low-level input voltage    0       1.5     Volts
High-level input voltage   3.5     40      Volts    not higher than supply

Vibrato Output
Open collector output with same specs as driver outputs, provided at the 40-pin headers.
A square wave of 0 to 10Hz is generated in response to "Modulation Bender"
channel node message. A value of zero turns this output off.
This output can be used to control a soleniod driven vibrato or "Leslie".

PWM Outputs
Four outputs with same specs as driver outputs, provided at the 40-pin headers.
A variable duty cycle square wave of 1000Hz is generated at each output.
The duty cycle at each output is controlled by channel node messages.

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Pin Descriptions

J1 I/O connector (40-pin header)
not available at this time.
J2 I/O connector (40-pin header)
not available at this time.
J3 I/O connector (40-pin header)
not available at this time.
J4 I/O connector (40-pin header)
not available at this time.
P1 MIDI IN connector (5-pin DIN)
not available at this time.
P2 MIDI OUT connector (5-pin DIN)
not available at this time.
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MIDI commands:
Note: numbers are hexadecimal.
k is channel number 0-F; 0 is channel 1, F is channel 16

Channel voice messages:

Bytes                   Description

8k nn vv                Note Off event, running status accepted

9k nn vv                Note On event (vv=0: Note Off) running status accepted

Ek vv vv                Pitch bend change (lsb first) NOT IMPLEMENTED

note: in output mode, the UM1 ignores the velocity value in note events, except if zero.
      in input mode, the UM1 uses a mid-velocity value (40hex) when sending note events.

Channel Mode Messages:

Bytes                   Description

Bk 7B 00                All Note Off event

Bk 01 vv                Modulation Bender (Vibrato), no bending is 0

Bk 02 vv                Controller change, PWM output 1

Bk 03 vv                Controller change, PWM output 2

Bk 04 vv                Controller change, PWM output 3

Bk 05 vv                Controller change, PWM output 4

System Real-Time Messages:

Bytes                   Description

FF                      Reset (all notes Off)
Reset all receivers in the system to
power-up status.

FE                      Active Sensing.
Use of this message is optional.  When
initially sent, the receiver will expect
to receive another Active Sensing message
each 300ms (max), or it will be assume
that the connection has been terminated.
At termination, the receiver will turn off
all voices and return to normal (non-
active sensing) operation.

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Ordering Information

UM1
Price: $249
UM1-P
Price: $279

UM1 available august 96
For quantity pricing, contact us at info@octetdesign.com

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© Copyright 1996 Octet Design Corporation. All Rights Reserved.

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