National Semiconductor Corporation

Simon J Levy

Donald B Alpert

A method for detecting and handling memory-mapped I/O in a pipelined data processing system is provided. The method uses two signals on the system interface: when the system generates a read bus cycle, it activates an output signal if certain I/O requirements are not satisfied; an input signal is activated when the reference is to a peripheral device that exhibits certain characteristics; when the system detects that both the input signal and the output signal are active, it discards the data read during the bus cycle, serializes instruction execution and regenerates the read bus cycle, this time satisfying the requirements for I/O such that the output signal is driven inactive.

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Kfar Saba, Israel

Simon J Levy