Capture combination action system for electronic organs

摘要

A microprocessor controlled electronic capture combination action system for use in an electronic organ for selecting a predetermined combination of stops to define the organ voicing. The system includes a plurality of stop tabs for setting and resetting the stops, a plurality of pistons for setting a desired combination of stops to a predetermined condition, a random access memory for storing data associated with a selected combination of stops, a read only memory containing a permanently stored operating program incorporating a plurality of operating instructions, an indicator light associated with each of the stop tabs and a microprocessor responsive to the operating instructions. The stop tab and pistons are continually and sequentially scanned to detect the contact closures. Actuated stop tabs cause the associated stops to be selected and the indicator lights illuminated. Information corresponding to a selected combination of stops for a selected one of the pistons is stored in the random access memory and may be recalled at will by closing the appropriate piston. The recalled data is used to select the combination of stops and illuminate the associated indicator lights. The system also includes a manually operable crescendo shoe which may be used to actuate a plurality of predetermined combinations of the stops in response to designated positions of the shoe. In a preferred embodiment, a crescendo circuit is used to cause a delayed interrupt signal to the operating program to provide a count which is compared against stored values associated with particular stop combinations. The crescendo shoe also includes a circuit for adding hysteresis to the crescendo shoe position. The operating program incorporates a debounce routine for eliminating false contact closures caused by switch bounce in the stop tabs such that the switch contacts must remain in a particular state for a number of successive scans before the switch closure will be detected.