Memory switching circuit for fetching microcomputer instruction

Abstract

Abstract PURPOSE:To select a state before which address is fetched as to its instruction, by storing the information for switching a memory by an address or the next address, in a register. CONSTITUTION:When an address from a microcomputer 1 coincides with a prescribed address, an address decoder supplies a coincidence signal to an address coincidence signal control part 17. The control part 17 is made active by an FF 14 which responds to the L output of a register 12 for storing the memory switching information, and outputs directly a coincidence output from a decoder 9. Subsequently, a memory switching part 4 separates a bus 5 from a bus 3, connects an instruction fetching memory 2 to the bus 3, and when the output of the register 12 is H, an active signal is outputted at the time of the next clock. When the decoder 9 is reset and the coincidence signal is not generated, the memory 6 for an instruction is selected. According to them, a state before which address is fetched as to its instruction can be selected, and an effective program debug is executed.

Inventors

• 👤 Kazuyoshi Kuwabara
• 👤 桑原　一悦

Bibliographic Details