| 摘要 |
A computer system is designed for use with a removable and insertable program source, such as a ROM cartridge 9 or floppy disk 12, and includes a CPU 1 for executing stored program instructions either directly from the ROM cartridge or after being read into a RAM memory 3. A video/sound generating chip 2 provides basic features open to all programs and enhanced features open only to selected programs. Access to the enhanced features is controlled by comparing a sequence of bytes outputted by the CPU in response to the program instructions with a reference sequence provided by a pseudo-random sequence generator (Figure 2), and enabling the enhanced features in dependence upon the result of the comparison. <IMAGE> |
