A microcomputer selectively operable in a first mode or a second mode comprises a first read-only memory for storing a first program to be executed in the first mode, a second, programmable read-only memory for storing a second program to be executed in the second mode, an input circuit for inputting...http://www.google.com.hk/patents/US5068783?utm_source=gb-gplus-share專利 US5068783 - Microcomputer having a built-in PROM for storing an optional program
