8088 Datasheet, PDF (10/30 Pages) Intel Corporation – 8-BIT HMOS MICROPROCESSOR

8088
Bus Operation
The 8088 address data bus is broken into three
parts the lower eight address data bits (AD0 –
AD7) the middle eight address bits (A8–A15) and
the upper four address bits (A16–A19) The ad-
dress data bits and the highest four address bits are
time multiplexed This technique provides the most
efficient use of pins on the processor permitting the
use of a standard 40 lead package The middle eight
address bits are not multiplexed i e they remain val-
id throughout each bus cycle In addition the bus
can be demultiplexed at the processor with a single
address latch if a standard non-multiplexed bus is
desired for the system
Each processor bus cycle consists of at least four
CLK cycles These are referred to as T1 T2 T3 and
T4 (See Figure 8) The address is emitted from the
processor during T1 and data transfer occurs on the
bus during T3 and T4 T2 is used primarily for chang-
Figure 8 Basic System Timing
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