Semiconductor integrated circuit operable and programmable at multiple

Abstract

Any one of the internal circuits of a semiconductor integrated circuit is made to operate both at a relatively high operating voltage having a predetermined allowable range and at a relatively low operating voltage also having a predetermined allowable range. The operating voltage is supplied from the outside. Moreover, the operating conditions of the internal circuits constituting the semiconductor integrated circuit are individually set restrictive to the relatively high operating voltage having a predetermined allowable range and to the relatively low operating voltage having a predetermined allowable range. The semiconductor integrated circuit is made to operate selectively at these operating voltages. Since the internal circuits are operated at these two kinds of operating voltages, an arrangement of internal circuits can be simplified and at the same time the semiconductor integrated circuit is usable in not only the conventional system but also a low-voltage one. Moreover, an operating method of the sort that conforms to specifications restrictive to both the relatively high operating voltage as used in the conventional system and the low-voltage system renders extendable a range of uses of such a semiconductor integrated circuit simple in construction.