| 摘要 |
<p>A memory cartridge according to this invention is mounted removably to a D processing device such as a portable electronic game machine containing a CPU, and contains a programmable ROM (PROM) and a bank switching circuit, and an external RAM is contained in the bank switching circuit. The external RAM is backed up by a cell. First and second key data are previously written into the PROM. After power supply is switched on, a reset signal is outputted when the power-supply voltage reaches a given value. When the first key data is read from the PROM and also a reset signal is outputted the external ROM becomes accessible by the CPU. When and after the second key data is read from the PROM, access by the CPU to the external RAM is prohibited.</p> |
