| 摘要 |
<p>PURPOSE:To mask a data signal by an address unit and to inhibit writing in the PROM by providing the PROM storing protect information to mask a data signal to a memory cell at the time of writing. CONSTITUTION:When a signal PRT is '1', a buffer 15 performs the data transmission between a buffer 16 and an external data bus, and a buffer 16 performs the data transmission between a memory cell array 12 and the buffer 15. The access to a memory cell array 11 is not performed because CE='1 and OE'=1 are always constant, and CE/OE are inputted to a CE', further, an OE is inputted as it is to an OE'. Thus, a memory cell array 12 can perform programming and verification from the external data bus similar to the memory cell array 11. At this time, the CE' is always '1', a signal masking the data signal outputted from the buffer 15 is not outputted, and the memory cell array is not influenced.</p> |
