PURPOSE: To execute characteristic evaluation or debugging through the use of a general purpose measuring instrument by adding a function to invalidate selectively the stoppage of transfer operation corresponding to the set number of transfer data.

CONSTITUTION: When a control signal CA is turned into a low level, the comparing operation of a comparator is invalidated, and even if the number of transfer data set in a register coincides with the count value of a counter, coincidence output is nor formed. Accordingly, it results practically in the same result that the upper limit value of the number of transfer data is removed, and since a counter control circuit continues to output a count instruction signal to the counter, and in response to this, a buffer RAM control circuit continues to access a buffer RAM, the data transfer is executed continuously and repeatedly. Since data transfer operation by the continuous access of the buffer RAM is executed continuously in this way, the characteristic evaluation or the debugging of data transfer equipment can be easily executed through the use of the general purpose measuring instrument.