Sequential Pro One - Page 52

The interface is compatible with standard TTL logic, where a 0 is signified by less than
0.8V and a 1 by greater than 2.5V. It accepts six data bits (DO through D5). This allows
the numbers 0 through 43 (decimal) to convert to over five octaves of "keyboardn
control when latched to the internal digital-to-analog converter (DAC) by the active
low -DAC EN pulse. The GATF is, exercised via a bit at pin 7.
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5. To play notes on the probe, the system driving it will have to do some-thing like
the following. (The way in which these events happen i$ not so important as their
sequence.) At the start, the analog KYBD CV output from the DAC (which controls the
oscillators and filter) is unknown. Nothing is heard from the Pro-One because the
envelope generators are not being gated. First the system somehow decides what key
(out of 63) it wants to play. It then sets up the key number in binary form on DO-D5,
(This might be done with a six-bit output port.) -DAC EN is normally high. To latch the
key data to the DAC, -DAC EN Is momentarily forced low. Data is then latched on the
rising edge of this pulse. For practical purposes a delay of 20 microseconds will allow
the
DAC time to "settletf (worst-case). At this point, GATE can go high, triggering the
envelope generators,
When the note is to be turned off, it is likewise advisable to turn
the GATE off (low) before again strobing the DAC.
6. To return the Pro-One to normal operation, unplug your system from 5101, remove
R1182, cut the jumper installed in step 3 and carefully re-install U113, 8021.
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