Abstract: An automatic testing instrument determines the operational status of an equipment under test on a real time basis by first generating from a stimulus memory a pattern for stimulating the equipment which, when stimulated by the pattern, sends out a response pattern, which is transmitted back to the automatic testing instrument. The testing instrument then takes the received response pattern and compares it with a pre-determined pattern stored in a comparator. If the response pattern differs from the expected pattern, an error signal is sent to indicate to the user of the testing instrument that the equipment under test is operating erroneously, for that particular pattern.

Abstract: By using a combination memory, shift register, logic gates and buffers, a stimulator used in an automatic testing instrument is able to provide two data rates for stimulating different equipment under test. The fast data rate is obtained by serially shifting parallel inputted data from the memory at a much faster rate than the operational speed of the memory. To accommodate equipment having a lower operating frequency, stimuli are transmitted to the equipment in a parallel mode.

Abstract: In an automatic testing instrument, to store responses educed from an equipment (4) under test in response to stimuli sent thereto, a response memory (16) is used. This response memory includes two serial/parallel shift registers (Z5, Z4), a buffer (Z2), a static RAM (Z3) and an input/output buffer (Z1). The response memory is capable of accepting the data bits being transmitted by the equipment under test at different data rates, corresponding to either serial or parallel inputted data bits.