| 摘要 |
<p>PURPOSE:To cope with changes of the contents of storage without changing the contents of a mask ROM by adding an address decoder and a storage to a storage circuit containing the mask ROM. CONSTITUTION:An address decoder 2 which receives supply of an address signal equal to the address of a mask ROM 1 and a storage 3 are set in parallel to the ROM 1. The read outputs of the ROM 1 and the storage 3 are delivered via an OR gate 6 as well as AND gates 6 and 5 which are controlled by the control signal CD. In such constitution, it is possible to cope substantially with changes of the storage contents without changing the contents of the ROM 1.</p> |
