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A RAM based EPROM simulator that allows a microprocessor such as the 8085 to switch between memory banks uses a flip-flop and an octal buffer. The circuit can switch between two memory banks, each consisting of both ROM and RAM addresses. A circuit diagram of the simulator is included.

A build-it-yourself 8048 microprocessor emulator costing $30 can interface with a standard terminal. It can set an unlimited number of breakpoints in the 2K program memory space. It emulates almost all hardware features with some compromises. A bank-switched memory has a 2K monitor bank and a 2K application bank. The monitor program is entered when an interrupt occurs. A smaller version can be built with fewer parts. Commands are accepted by a command monitor. The system can run cyclic redundancy check and analog to digital convertor applications. Circuit diagrams of the emulator and the small emulator; a block diagram of the interrupt logic; diagrams of the emulator, the emulator address space, interrupt timing, and an analog to digital convertor; a table of emulator commands; and program listings of a terminal program and the monitor are included.

Memory bank switching is used on an 8-bit microcomputer to access an address space greater than 64K. Direct addressing is limited to 64K while bank switching can address up to 16 megabytes. Multiplexing is where the 8-bit address line is used to access a 16-bit address space. Bank switching is achieved on a 8080 by using the 256 I-O ports to access individual banks of memory which can be up to 64K each.