Verkehrsampel-Modul (Modellbau, 4011, 4001)

This, the third article in the SC/MP series, introduces the memory extension card, which, in addition to containing¾ k of RAM and ½ k of PROM, also houses the multiplexer and priority encoder. The latter hardware allows the SC/MP to handle interrupt requests from more than one peripheral device. The article also examines the software involved in interrupt operations.