| 摘要 |
PURPOSE:To provide the write protect for one-chip CPU which can surely limit write to a PROM and can considerably improve the security of an IC card when this write protect is applied for the field of the IC card, etc. CONSTITUTION:An independent external terminal (e) is newly provided to apply a write control signal 7 for PROM to a PROM 12. This external terminal (e) and an external terminal (d) for a write control signal 4 for a CPU 10 are connected through a write protect switch 13 and a cut jumper 14. When the write protect switch 13 is switched to a write enable state and the write control signal 4 for the CPU 10 and the write control signal 7 for PROM are connected, data can be written into the PROM 12. When the cut jumper 14 is disconnected, no data can not be permanently written into the PROM 12 since the write control signal 4 and the write control signal 7 for PROM are not connected afterwards. |
