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LOCALBU51NTERFACE
Table
3-S.
Generation
of
BHE#, BLE#, and
A1
from Byte Enables
InteI386'·
OX
Microprocessor Signals
16-Bit Bus Signals
Comments
BE3#
BE2# BE1#
BEO#
A1
BHE#
BLE#
(AO)
H* H*
H* H*
x
x x x -
no
active bytes
H
H
H,
L L
H L
H H L
H L L H
H H L L L
L L
H
L H H
H H L
H*
L*
H*
L*
x x
,
x
x-not
contiguous bytes
H L L H
L L H
H
L L L L L
L
L
H
H
H H L H
L*
H* H*
L*
x x x
x-not
contiguous bytes
L*
H*
L* H* x x x
x-not
contiguous bytes
L*
H*
L* L*
x
x x
x - not contiguous bytes
L
L
H
H H L L
L*
L* H* L* x
' x
x
x - not contiguous bytes
L
L L H L L
H
L
L L L L L L
BLE# asserted when
00-07
of 16-bit bus
is
active.
BHE# asserted when
08-015
of 16-bit bus
is
active.
A1
low for
all
even words;
A1
high for all odd words.
Key:
x = don't care
H
= high voltage level
L = low voltage level
*
= a non-occurring pattern of Byte Enables; either none
are
asserted, or the pattern has Byte
Enables asserted for non-contiguous bytes
Table 3-6. Byte Enables during B516 Cycles
First Cycle
Second Cycle
!3E3#
BE2#
BE1#
BEO#
BE3# BE2# BE1#
BEO#
High High
High Low No second
cycle
High
High Low High
No
second cycle
High High Low
Low
No
second cycle
High Low High
High
No
second cycle
High Low
Low High High Low High High
High
Low Low Low High Low High High
Low High
High High No second
cycle
Low Low High
High
No
second cycle
Low Low
Low High
Low
Low High High
Low Low Low Low Low Low High High
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