AMD AMD-K6-2/500AFX Data Sheet - Page 131
M/IO# (Memory or I/O
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21850J/0-February 2000 Preliminary Information AMD-K6®-2 Processor Data Sheet 4.34 M/IO# (Memory or I/O) Summary Driven and Floated Output The processor drives M/IO# during a bus cycle to indicate whether it is addressing the memory or I/O space. If M/IO# = 1, the processor is addressing memory or a memory-mapped I/O port as the result of an instruction fetch or an instruction that loads or stores data. If M/IO# = 0, the processor is addressing an I/O port during the execution of an I/O instruction. In addition, M/IO# is used to define other bus cycles, including interrupt acknowledge and special cycles. See Table 25 on page 126 for more details. M/IO# is driven off the same clock edge as ADS# and remains in the same state until the clock edge on which NA# or the last expected BRDY# of the cycle is sampled asserted. M/IO# is driven during memory cycles, I/O cycles, special bus cycles, and interrupt acknowledge cycles. M/IO# is floated off the clock edge that BOFF# is sampled asserted and off the clock edge that the processor asserts HLDA in response to HOLD. Chapter 4 Signal Descriptions 111