Intel 80C186EA User Manual page 111

BUS INTERFACE UNIT
CLKOUT
ALE
S2:0
AD15:0
[AD7:0]
[A15:8]
A19:16
BHE
[RFSH = 1]
NOTES:
1. The AD15:0 [AD7:0] bus can be floating, driving a previous write data value,
or driving the next instruction prefetch address value. For an 8-bit device,
A15:8 either drives the previous bus address value or the next instruction
prefetch address value.
2. The AD15:0 bus, or AD7:0 and A15:8 buses for an 8-bit device, drive to a
zero (all low) at this time if Powerdown Mode is enabled. When Powerdown
Mode is not enabled, the AD15:0 [AD7:0] bus either floats or drives previous
write data, and A15:8 (8-bit device) continues to drive its previous value.
3. The AD15:0 bus, or AD7:0 and A15:8 buses for an 8-bit device, drive to a
zero (all low) at this time if Idle Mode is enabled. When Idle Mode is not
enabled, the AD15:0 [AD7:0] bus either floats or drives previous write data,
and A15:8 (8-bit device) continues to drive its previous value.
4. The A19:16 bus either drives zero (all low) or 8H (all low except A19/S6,
which can be high if the previous bus cycle was a DMA or refresh operation).
If either Idle or Powerdown Mode is enabled, the A19:16 bus drives zeros
(all low) at phase 1 of TI. Otherwise, the previous value remains active.
3-30
T1
011
Note 1 Note 2
Note 2 Note 2
Figure 3-25. HALT Bus Cycle
TI TI
Note 3
Note 3
Note 4
A1088-0A