Intel Embedded Intel486

EMBEDDED Intel486™ PROCESSOR HARDWARE REFERENCE MANUAL
7-12
Table 7-6. PLD Input Signals
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.
Table 7-7. PLD Output Signals
BS16# Word enable for 16-bit interface.
Table 7-8. Equation
BEN16 = ADS * BE2 * /BE1 * /BE0 * BS16 * /BS8
+ ADS * BE3 * /BE1 * /BE0 * BS16 * /BS8
+ /ADS * BEN16
;swapping upper 16-bits
Table 7-9. 32-Bit to 16-Bit Bus Swapping Logic Truth Table (Sheet 1 of 2)
Intel486™ Processor
(3)
8-Bit Interface
(1)
BE3# BE2# BE1# BE0# BEN16# BEN8UH# BEN8UL# BEN8H# BHE#
(2)
A1 A0
0000 1 1 1 1 1 0 1
1000 1 1 1 1 1 0 1
0100
†
11 1 1XXX
1100 1 1 1 1 1 0 1
0010
†
01 1 10X0
1010
†
01 1 1XX0
Inputs Outputs
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.