Little Blue Limited Partnership

Walter Broedner

Wendell B Sander

Dick Huston

Clifford Huston

A port emulator circuit implemented on an Apple II peripheral card which enables MS-DOS programs designed to run on an 8086 microprocessor based IBM type personal computer to perform input/output operations on peripheral devices used by 6502 microprocessor based Apple II computers. As the 8086 requires I/O, a state machine, which forms part of the port emulator, performs the required bus arbitration between the 8086 and the 6502 and informs the 6502 of pending requirements of the 8086. The 6502 determines the type of I/O required, and using Apple II hardware resource, performs the I/O operation. The 6502 also places status information concerning the I/O operation in a portion of RAM on the peripheral card, which RAM location emulate the I/O registers found on IBM personal computers.

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Saratoga, CA, United States of America

Walter Broedner