macro 30 with a memory the feature macro 58 is coupled to the base macro 30 by connecting the address line 0 62 address line 1 64 and feature macro used 70 connection points 52 of a second port 50 on the base macro 30 to the address line 0 62 39 address line 1 64 39 and feature macro used 70 39 connection points respectively of the feature macro 58 the serial port in 66 and serial port used 68 connection points 52 on the base macro are unconnected an alternative method for connecting a feature macro f to a base macro 30 is shown in fig6 and 7 in this embodiment the discrete connection points 52 of fig4 and 5 are replaced by a set of concentric continuous connection paths 80 which extend around the periphery of the base macro 30 in this manner a feature macro f may be connected at any point around the periphery of the base macro 30 by connecting the connection points 82 of the feature macro f to corresponding connection paths 80 on the base macro 30 using appropriate conductive paths 84 the base macro 30 may be provided with multiple sets of the concentric connection paths 80 to allow a plurality of feature macros to be respectively connected thereto alternately multiple feature macros may be connected to a single set of connection paths 80 if the base macro 30 is capable of differentiating between the plurality of feature macros further connection paths which extend partially around the periphery of the base macro 30 in one or more locations may also be used without departing from the intended scope of the present invention the foregoing description of the present invention has.