Intel Embedded Intel486 Hardware Reference Manual page 184

EMBEDDED Intel486™ PROCESSOR HARDWARE REFERENCE MANUAL
BS16# Either from a 16-bit device or from system logic which indicates a 16-bit transfer.
BE3#–BE0# Byte enable inputs from Intel486™ processor. In 16-bit mode, the external logic should
look at BE0# and BE1# only.
ADS# Address strobe from an Intel486 processor indicating a valid CPU cycle.
BS16# Word enable for 16-bit interface.
BEN16 = ADS * BE2 * /BE1 * /BE0 * BS16 * /BS8
+ ADS * BE3 * /BE1 * /BE0 * BS16 * /BS8
+ /ADS * BEN16
Table 7-9. 32-Bit to 16-Bit Bus Swapping Logic Truth Table (Sheet 1 of 2)
Intel486™ Processor
BE3# BE2# BE1# BE0#
0 0 0
1 0 0
0 1 0
1 1 0
0 0 1
1 0 1
Inputs
NOTES:
1. X implies "do not care" (either 0 or 1).
2. BHE# (byte high enable) is not needed in 8-bit interface.
†
3. indicates a non-occurring pattern of byte enables; either none are asserted or the pattern has byte
enables asserted for non-contiguous bytes.
7-12
Table 7-6. PLD Input Signals
Table 7-7. PLD Output Signals
Table 7-8. Equation
(3)
BEN16# BEN8UH#
0 1 1
0 1 1
†
0 1 1
0 1 1
†
0 0 1
†
0 0 1
(1)
8-Bit Interface
BEN8UL# BEN8H#
1 1
1 1
1 1
1 1
1 1
1 1
Outputs
;swapping upper 16-bits
(2)
BHE# A1 A0
1 0 1
1 0 1
X X X
1 0 1
0 X 0
X X 0