Nvis 5586A
Nvis Technologies Pvt. Ltd.
15
8086 Maximum Mode Block Diagram
8288 Bus Controller – Bus Command and Control Signals:
8086 does not directly
provide all the signals that are required to control the memory, I/O and interrupt interfaces.
Specially the WR*, M/IO*, DT/R*, DEN, ALE and INTA, signals are no longer produced by
the 8086. Instead it outputs three status signals S0*, S1*, S2* prior to the initiation of each
bus cycle. This 3- bit bus status code identifies which type of bus cycle is to follow.
S2*S1*S0* are input to the external bus controller device, the bus controller generates the
appropriately timed command and control signals.
The 8288 chip receive the status signal S2*, S1* and S0* and the clock from 8086. Theses
status signals are decoded to generate MRDC* (Memory read command), MWTC* (memory
write command), IORC* (I/O read command), IOWC* (I/O write command), INTA*
(Interrupt acknowledgement) signal. In addition, it can generate advanced memory and I/O
write signals AMWC* (Advanced memory write command), AIOWC* (Advanced I/O write
command) that are enabled one clock cycle earlier than the normal write control signals
because some device require wider cycle.
Summary of Contents for 5586A
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