Abstract: Apparatus and method for monitoring transactions on a high speed interface us and for selectively storing information about such transactions together with the time of such transaction and the state of the automaton. The apparatus comprises two parallel memories for respectively storing a regular table and a default table, and a memory selector for choosing between the table data of the two memories. A bus trap stores data information obtained from the bus and compares the stored information with a stored data template. A transition detector receives control signals from the bus and generates clock signals used by other system elements upon the detection of a transition. A hash coder utilizes a hash key together with state information to generate an address for entering the regular table memory. A state latch stores an address provided by the memory selector for the default table.