A versatile computer-controlled biological stimulus sequencer.

A computer-controlled stimulus sequencer has been developed. This device can be controlled by several commonly available, inexpensive 8-bit microcomputers in which the address, data, and control lines are externally accessible. Although the Apple implementation has been described, a similar interface has also been devised for the Radio Shack Color Computer. The hardware relies on the Rockwell Versatile Interface Adapter (VIA) chip (which has two 16-bit timers capable of functioning as frequency dividers, event counters, or one-shots) and a 12-bit digital-to-analog converter (DAC) chip. This hardware combination, along with software written in Basic and machine language (stored in an EPROM for turn-key operation), allows creation of a large number of unique trains that can be chained together in any sequence. This is aided by storing the train characteristics economically in the computer memory and chaining different train parameters in a link-list. Several train parameters can be incremented or decremented manually by a pair of keys. The amplitude of the train can be changed manually or under program control. Once created, the trains can be edited on the run or deleted from the sequence. The device also generates a trigger pulse that can be referenced to any pulse in a train and can be used to pretrigger an oscilloscope. The software has provision for detecting an external signal, and this information can be used to modify train parameters. The interface is interrupt driven and therefore does not require continuous use of the Basic interpreter.(ABSTRACT TRUNCATED AT 250 WORDS)