Integrated circuit and method of automatically selecting an internal or an external non-volatile memory as a source of program code responsive to presence or absence of the external non-volatile memory

Abstract

The present invention is a semiconductor device that includes a DRAM and an internal mask ROM that are implemented on a single integrated circuit substrate. The semiconductor further includes a terminal coupled to an external ROM and a selector for choosing an external ROM or an internal mask ROM for program code loading. If an external ROM is coupled to the aforementioned terminal, the external ROM is given precedence for use in the loading of the aforementioned program code. The control method of the present invention pertains to a semiconductor device including a DRAM, an internal mask ROM, a terminal coupled to an external ROM, a selector for choosing the first path led from the internal mask ROM or the second path led from the terminal, and a coupling determiner deciding whether or not the terminal is coupled to the external ROM. The control method includes the steps of: (a) deciding whether or not the terminal is coupled to the external ROM; (b) selecting a first path when a terminal is not coupled to the external ROM or a second path when the terminal is coupled to the external ROM; and (c) loading a program code from either the internal mask ROM or the external ROM.