Wait Mode in Areas Where Wait-State Controller is Disabled
External three-state access areas in which the wait-state controller is disabled (ASTn = 1, WCEn =
0) operate in pin wait mode 0. The other wait modes are unavailable. The settings of bits WMS1
and WMS0 are ignored in these areas.
Pin Wait Mode 0: Wait states can only be inserted by
WAIT
pin control. During access to an
external three-state-access area, if the
WAIT
pin is low at the fall of the system clock (ø) in the T
2
state, a wait state (T
W
) is inserted. If the
WAIT
pin remains low, wait states continue to be
inserted until the
WAIT
signal goes high. Figure 6-12 shows the timing.
Figure 6-12 Pin Wait Mode 0
ø
pin
Address bus
Data bus
AS
RD
HWR
Data bus
,
LWR
T
1
T
2
T
W
T
W
T
3
Inserted by signal
Write data
*
*
Read data
Read
access
Write
access
External address
WAIT
WAIT
Note: Arrows indicate time of sampling of the pin.
*
WAIT
*
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