| 摘要 |
PROBLEM TO BE SOLVED: To provide a PROM(programmable read only memory) circuit for writing without using any SRAM(static random access memory) for writing into a flash memory or without frequent switching between a flash memory and a PROM. SOLUTION: This PROM circuit for writing into a flash memory using a PROM 3 for writing into a flash memory 2 in a microprocessor system using the flash memory as a program storing device, is equipped with the PROM accessible at two positions, that is, an address A6 accessed when power is turned on and switchable to a flash memory and an address B7 accessible at all times independently of the flash memory existing in a separate space, a switching means SW1 for allocating an area of an address A to the PROM or the flash memory when resetting, an access means capable of accessing two positions, the address A and an address B, on the PROM, and a writing means for switching from the PROM to the flash memory and writing PROM data in the address B into the flash memory.
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