4-7
BUS OPERATION
Table 4-5. Generating A1, BHE# and BLE# for Addressing 16-Bit Devices
Intel486™ Processor 8-, 16-Bit Bus Signals
Comments
BE3# BE2# BE1# BE0# A1
3
BHE#
2
BLE# (A0)
1
1
†
1
†
1
†
1
†
xx x x–no asserted bytes
11100 1 0
11010 0 1
11000 0 0
10111 1 0
1
†
0
†
1
†
0
†
xx x x–not contiguous bytes
10010 0 1
10000 0 0
01111 0 1
0
†
1
†
1
†
0
†
xx x x–not contiguous bytes
0
†
1
†
0
†
1
†
xx x x–not contiguous bytes
0
†
1
†
0
†
0
†
xx x x–not contiguous bytes
011100
0
†
0
†
1
†
0
†
xx x x–not contiguous bytes
00010 0 1
00000 0 0
NOTES:
1. BLE# asserted when D7–D0 of 16-bit bus is asserted.
2. BHE# asserted when D15–D8 of 16-bit bus is asserted.
3. A1 low for all even words; A1 high for all odd words.
KEY:
x = don't care
†
= a non-occurring pattern of byte enables; either none are asserted or the pattern has byte
enables asserted for non-contiguous bytes
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