Intel Embedded Intel486 Hardware Reference Manual page 71

Table 4-5. Generating A1, BHE# and BLE# for Addressing 16-Bit Devices
Intel486™ Processor
BE3# BE2# BE1#
† † †
1 1 1
1 1 1
1 1 0
1 1 0
1 0 1
† † †
1 0 1
1 0 0
1 0 0
0 1 1
† † †
0 1 1
† † †
0 1 0
† † †
0 1 0
0 1
† † †
0 0 1
0 0 0
0 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
8-, 16-Bit Bus Signals
3
BE0# A1 BHE#
†
1 x x
0 0 1
1 0 0
0 0 0
1 1 1
†
0 x x
1 0 0
0 0 0
1 1 0
†
0 x x
†
1 x x
†
0 x x
1 1 0
†
0 x x
1 0 0
0 0 0
2 1
BLE# (A0)
x x–no asserted bytes
0
1
0
0
x x–not contiguous bytes
1
0
1
x x–not contiguous bytes
x x–not contiguous bytes
x x–not contiguous bytes
0
x x–not contiguous bytes
1
0
BUS OPERATION
Comments
4-7