The HD404054 Series and HD404094 Series are HMCS400-series microcomputers designed to increase program productivity with large-capacity memory. Each microcomputer has three timers, one serial interface, comparator, input capture circuit. The HD404054 Series includes three chips: the HD404052 with 2-kword ROM; the HD404054 with 4kword ROM; and the HD4074054 with 4-kword PROM (ZTATTM version). Also, the HD404094 Series includes three chips: the HD404092 with 2-kword ROM; the HD404094 with 4-kword ROM; and the HD4074094 with 4-kword PROM (ZTATTM version). The HD4074054 and HD4074094 are PROM version (ZTATTM microcomputers). Program can be written to the PROM by a PROM writer, which can dramatically shorten system development periods and smooth the process from debugging to mass production. (The ZTATTMversion is 27256-compatible.)