Importance

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Abstract

Each internal circuit of a semiconductor integrated circuit operates at both a relatively high operating voltage having a predetermined allowable range and a relatively low operating voltage also having a predetermined allowable range. The operating voltage is externally supplied. Operating conditions of 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 operable selectively at these operating voltages. Since the internal circuits are operated at two operating voltages, an arrangement of internal circuits can be simplified while the semiconductor integrated circuit is concurrently 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 of both the relatively high operating voltage as used in the conventional system and the low-voltage system renders a simply constructed integrated circuit with an extendable a range of uses.

First Claim