| 摘要 |
<p>PURPOSE:To improve the transfer capacity of an external data bus by containing an extended data bus buffer, an extended data bus and an extended data bus controller in an external data bus interface part against a microprocessor. CONSTITUTION:With respect to a CPU part 1 of the same constitution as a 16-bit microprocessor, an extended data bus buffer 3, an extended data bus 4 and an extended data bus controller 5 are provided. In a program read cycle and a data read cycle to a memory, 32-bit data fetched by a single memory read cycle by the extended data bus 4 is stored temporarily in the extended data bus buffer 3. Subsequently, the CPU part 1 fetches successively 16-bit data stored in the upper and the lower parts of the extended data bus buffer 3. These read/write accesses to the memory and the access to the extended data bus buffer 3 from the CPU part 1 are controlled by the extended data bus controller 5. In such a way, the external data bus width is extended, and the transfer capacity can be enhanced.</p> |
