| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a high density multi-level ROM by forming a multi-level cell programmed at a direct memory access mode. SOLUTION: A memory cell comprises floating gate MOS transistors respectively arranged on intersected points between rows and columns, and all source terminals are connected to a common ground line. Further, all drain terminals are connected to a common row line or bit line, and all gate terminals are connected to an answering common column line or word line. A DMA(direct memory access) mode enable circuit 2 controls a storage directly through the bit line from the outside, and outputs multi-level information read out by a read-out circuit block 3 connected to a column address decoder CDEC. By correctly comparing a programmed cell setting reference value, read-out/collation step work becomes correct, and the high density multi-level ROM is formed.</p> |
