| 摘要 |
PURPOSE:To set arbitrarily a program start address with the simple constitution. CONSTITUTION:At the time of resetting, an address signal set by an initial address generating circuit is selected and outputted to a system bus. For instance, '0100' is outputted to four bits of 'A19, A18, A17 and A16'. Assuming that 16 bits of the reset start addresses A15-Aphi of a CPU 1 are 2000 address, a 42000 address is outputted to a system bus 7, and a program is executed at 42000 address. Afterwards, '0100' is outputted to four bits of 'A19, A18, A17 and A16' of the address bus of the CPU 1, it is decoded to generate a control signal from a control signal generating circuit 4. Then the signal is inputted to a selecting circuit 3, and A19-A16 signals of the address bus of the CPU 1 are outputted to the system bus 7. From now on, the A19-A16 of the address bus of the CPU are outputted to the A19-A16 of the system bus. |
