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Wait Modes in Areas Where Wait-State Controller is Enabled: External three-state access
areas in which the wait-state controller is enabled (ASTn = 1, WCEn = 1) can operate in pin wait
mode 1, pin auto-wait mode, or programmable wait mode, as selected by bits WMS1 and WMS0.
Bits WMS1 and WMS0 apply to all areas, so all areas in which the wait-state controller is enabled
operate in the same wait mode.
• Pin Wait Mode 1
In all accesses to external three-state-access areas, the number of wait states (T
bits WC1 and WC0 are inserted. If the WAIT pin is low at the fall of the system clock (φ) in
the last of these wait states, an additional wait state is inserted. If the WAIT pin remains low,
wait states continue to be inserted until the WAIT signal goes high.
Pin wait mode 1 is useful for inserting four or more wait states, or for inserting different
numbers of wait states for different external devices.
If the wait count is 0, this mode operates in the same way as pin wait mode 0.
Figure 6.13 shows the timing when the wait count is 1 (WC1 = 0, WC0 = 1) and one additional
wait state is inserted by WAIT input.
φ
WAIT
pin
Address bus
AS
RD
Read
access
Data bus
HWR, LWR
Write
access
Data bus
Note:
Arrows indicate time of sampling of the
*
Inserted by
wait count
T
T
1
2
External address
WAIT
pin.
Figure 6.13 Pin Wait Mode 1
Section 6 Bus Controller
Inserted by
WAIT
signal
T
T
W
W
*
*
Read data
Write data
Write data
Rev. 3.00 Mar 21, 2006 page 133 of 814
) selected by
W
T
3
REJ09B0302-0300
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