Method and apparatus for circuit testing with ring-connected test
instrument modules. A system for controlling one or more test instruments
to test one or more integrated circuits includes a master clock and a
controller. The test instruments are connected to form a communication
ring. The master clock is connected to each test instrument and provides
a clock signal to the one or more test instruments. The controller is
connected to the communication ring and is configured to align counters
of test instruments to derive a common clock time value from the clock
signal. The controller is further configured to generate and send data
words into the communication ring to carry the data words to each test
instrument. The data words includes at least one data word specifying a
test event to be performed, a common clock time value, and at least one
of the test instruments.