| 摘要 |
An expandable ROM module adapted for use with an existing ROM interface having a predetermined number of address lines to provide an expanded memory array of variable size. The expanded memory is divided into a plurality (T) of pages and a temporary storage device is provided to store page address data. The temporary storage device includes a T-bit page selection register, which receives address input from the ROM interface, and a mapping array, which has T entries, to direct address inputs to each page. Page address data are stored in the temporary storage device via a convert-read-to-write method, which utilizes read interface and read cycle to perform write operations. Several convert-read-to-write methods can be provided depending on the number of addresses that need to be reserved and the complexity of circuitry and programming that will be involved. Examples of the convert-read-to-write methods include: direct, direct but segmented, indirect and segmented, multiple-indirect and segmented. The indirect methods involve at least one index register, which is another temporary storage device.
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