Arrangement for determining the length of arbitrary shift registers

Abstract

A diagnostic arrangement is disclosed for determining the length of arbitrary shift registers not exceeding a maximum length. Knowledge of this length is an essential prerequisite for data manipulations by means of shift registers. Concerned are the reading of shift registers and the display of the contents stored in them, as well as the writing of arbitrarily selectable patterns into said shift registers. The arrangement proper includes circuitry connected to the shift register or test object for generating a test shift pattern of the length L.sub.max +K, with K.gtoreq.2, which pattern is made up of a defined bit configuration, for example, only binary ones, with a defined transition at the end facing the test object and which is shifted through the test object. Also provided is storage means of length L.sub.max +K, which is connected to the output of the test object and which, as the test shift pattern is shifted, accommodates the information of the length L.sub.x of the test object and the part L.sub.max +K-L.sub.x of the test shift pattern. The arrangement also includes a display means, whose individual fields are associated with one storage cell each of the storage means, so that its contents can be displayed and thus the data transition, for example, from zero to one, indicating the end of the shift register of unknown length, can be determined. From the subsequently determinable beginning and end of the shift register of unknown length, its actual length can be derived.