Patent ID: 7043615
Filing Date: 2006-05-09
Classification: G06F,G11C

Abstract:
1. A nonvolatile semiconductor flash memory comprising: a memory cell array containing a plurality of nonvolatile memory cells; a decoder driver to select a nonvolatile memory cell addressed from the memory cell array; and an access control circuit supplied with an input command and an input address; wherein the access control circuit compares access control information about an access control area limiting a specified access in the memory cell array with the input command and the input address supplied to the access control circuit, provides control to select a nonvolatile memory cell specified by the input address via the decoder driver when the input command and the input address do not comply with an access limited for an address control area, and provides control not to select a nonvolatile memory cell specified by the input address via the decoder driver when the input command and the input address comply with an access limited for the address control area; the access control information includes address information about an access-limited area and a limited access mode; information included in the access control information is specifiable by means of a command; the access control information has a first key provided in correspondence with the access-limited area; the access control circuit further compares the first key with an input key input together with the input command and the input address, provides control to select a nonvolatile memory cell specified by the input address via the decoder driver when the input key matches the first key or the input command and the input address do not comply with an access limited for the address control area, and provides control not to select a nonvolatile memory cell specified by the input address via the decoder driver when the input key does not match the first key and the input command and the input address comply with an access limited for the address control area; the first key included in the access control information is specifiable by means of a command; the access control information has a permitted access mode allowed when the input key does not match the first key; and the access control circuit provides control to select a nonvolatile memory cell specified by the input address via the decoder driver-even if the input key and the first key do not match and if the input command is included in the permitted access mode.