Fujitsu Corporation

Fujitsu Semiconductor Limited

Yasuhiro Onishi

Akira Kikutake

Kuninori Kawabata

Toshiya Miyo

Satoshi Eto

Masato Matsumiya

Toshikazu Nakamura

Junichi Sasaki

The data memory cell array and parity memory cell array in the memory cell array has a constitution that is capable of corresponding with a plurality of ECC code lengths. An input-side parity generation circuit that generates parities from write data, an output-side parity generation circuit that generates parities from read data, and a syndrome generation circuit that generates a syndrome bit that indicates an error bit from the read parity bits and generated parity bits are constituted so as to be capable of switching, according to the plurality of ECC code lengths.

Semiconductor memory device capable of changing ECC code length

Disclosed is a semiconductor memory device capable of arbitrarily setting an upper limit of the number of error corrections during a test operation. The semiconductor memory device has a counter, a register, and a comparison circuit. The counter counts the number of error corrections. The register, when an upper limit setting signal is externally inputted to change the upper limit of the number of error corrections, changes the upper limit. The comparison circuit compares the number of error corrections with the changed upper limit.

Semiconductor memory device

A normal write data selection circuit operates in the normal operation mode, and thus outputs data received through external data terminals to any one of regular cell arrays selected according to an address. A test write control circuit operates in the test mode, and thus writes test data into a regular memory cell at a location corresponding to a location of a parity memory cell into which test parity data are written in each of regular cell arrays. Therefore, since a common test pattern can be used to test both the regular memory cell and the parity memory cell, test cost can be curtailed.

Semiconductor memory

During a first data compression test mode which disables an error correction function, first test data are written to a first regular memory block. Second test data are written to not only a second regular memory block, but a parity memory block. By changing the number of bits distributed to the first and second test data (compression rate of data), a data compression test for a parity memory block can be performed without need to increase the number of test terminals. As a result, the test time can be decreased and the test cost can be decreased.

Semiconductor memory having error correction

Regular data inputted/outputted to/from external terminals is read/written to/from a regular cell array, and parity data is read/written from/to a parity cell array. Since the parity data is generated by a parity generation circuit, it is difficult to write a desired pattern to the parity cell array. The regular data and the parity data are exchanged with each other by a switch circuit, so that the regular data can be written to the parity cell array and the parity data can be written to the regular cell array. This enables the write of desired data to the parity cell array. A test of the parity data can be easily conducted. In particular, a leakage test or the like between memory cells can be easily conducted.

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Kawasaki, Japan

Yasuhiro Onishi