| 摘要 |
PURPOSE:To decrease a hardware quantity, by packing an address register which designates the addresses for both an ROM and an RAM, a circuit which switches the output between the RAM and ROM and a register which holds the control signal to control the switching circuit and the output of the switching circuit on a single chip. CONSTITUTION:An address is transferred to an ROM/RAM address register 12 via an internal bus 11. The output of the register 12 is fed to both an ROM13 and an RAM14 to give a simultaneous access to the ROM13 and RAM14. The outputs of the ROM13 and RAM14 are fed to a switching circuit 15. The circuit 15 performs the switching to the output of the ROM13 or the output of the RAM14 with a control signal 16. This switch output is held at an output holding register 17 and then transferred via the bus 11. Then the data input to the RAM is fed to an RAM input holding register 18 to be fed to the RAM. In such a way, it is possible to hold the outputs of both ROM and RAM at the same output holding register. Thus the hardware quantity can be decreased for the holding register. |
