AMD-K6 Datasheet, PDF (123/346 Pages) Advanced Micro Devices – AMD-K6 Processor

20695H/0—March 1998
Preliminary Information
AMD-K6^® Processor Data Sheet
5.33
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 19 on page 119 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 5
Signal Descriptions
105