Intel 386 manual LOCALBU51NTERFACE

LOCALBU51NTERFACE

Table 3-S. Generation of BHE#, BLE#, and A1 from Byte Enables

InteI386'·OX Microprocessor Signals					16-Bit Bus Signals
BE3#	BE2#	BE1#	BEO#	A1	BHE#	BLE# (AO)		Comments
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'tcare

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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