| 摘要 |
<p>PURPOSE:To make masking effective, by taking an address of a PROM the same address as a part of a mask ROM and reading out the content of the PROM when the said address is accessed. CONSTITUTION:An address signal ADS corresponding to the address given to all areas of the mask ROM 1 is provided for an address decoder 3. The PROM 2 having the same capacity as an area 1a a part of the ROM 1 is provided and the address of the PROM 2 is made the same as the area 1a of the ROM 1. A decoder 3 decodes the signal ADS and the address signal corresponding to the area 1a is applied to the PROM 2 and the content of storage is read out.</p> |
