5.5
5.5.2 ORGAN RHYTHM GENERATION
Applications
The rhythm generation diagram (Fig. 26) illustrates a simplified
version of how a microcomputer can be implemented with the AY-3-
8910 to provide a percussion instrument section for an electronic
(cont.) organ.
The microcomputer used in this case could be a GI PIC 1650 which
can be internally programmed to drive a series of AY-3-8910’s all
hardwired to an I/O port of the PIC. Each AY-3-8910 provides a
separate output envelope and frequency of the instrument it is to
synthesize.
The Rhythm Switch Matrix is used to select any preprogrammed
rhythm pattern and tempo from the PIC. The Instrument Select
switches allow manual in/out selection of the 8910’s via the A8 and A9
address lines providing additional instrument sound variations.
These switches are intended to be user-selected and mounted in a
convenient position on the instrument.
In addition, optional ROMs could be added to the PSG I/O ports,
saving microcomputer ports, to provide extra rhythm length or
number of patterns. These ROMs could also be replaced by EAROMs
to provide user rhythm programming from a modified Rhythm Switch
Matrix. The programmable rhythm feature could be used to add new
or original user rhythms to update the instrument.
Fig. 26 ORGAN RHYTHM GENERATION
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