Pin Auto-Wait Mode: If the
WAIT
pin is low, the number of wait states (T
W
) selected by bits
WC1 and WC0 are inserted.
In pin auto-wait mode, if the
WAIT
pin is low at the fall of the system clock (ø) in the T
2
state, the
number of wait states (T
W
) selected by bits WC1 and WC0 are inserted. No additional wait states
are inserted even if the
WAIT
pin remains low. Pin auto-wait mode can be used for an easy
interface to low-speed memory, simply by routing the chip select signal to the
WAIT
pin.
Figure 6-14 shows the timing when the wait count is 1.
Figure 6-14 Pin Auto-Wait Mode
ø
Address bus
Data bus
AS
RD
HWR
Data bus
,
LWR
T
1
T
2
T
3
T
1
T
2
T
W
T
3
*
*
Read data
Read data
Write data
Write data
Read
access
Write
access
Note: Arrows indicate time of sampling of the pin.
*
WAIT
External address
External address
WAIT
136
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