Real-time multichannel timer-A/D controller for electrophysiological investigations

Real-time multichannel electrophysiologic analysis calls for flexibility (the stimulus or the interstimulus can be deterministic as well as random, and the signal on each channel can be sampled at a different rate to minimize the cost of the digitized information) and fast line scanning so that all channels are scanned by the minimum time between two successive samples of input signals. To achieve these two objectives, a powerful, cost-effective electronic system has been designed. The characteristics of the system are as follows: (1) It is modular with maximally 16 analog channels per module. (2) Electronics is autonomous in the measurement data acquisition while it is under computer control in both phases of the system's initialization and the transfer of the measurement data (time instant of events, which may be contemporary events on different channels, the encoded address of the channel the electronics is serving, and the analog to digital conversion result of the signal at the input of the same channel). (3) The minimum and maximum channel scanning times are 1 and 5 clock periods (15 MHz), respectively. The maximum error on the event time measurement is 1 clock period.