HD6473032F16 Datasheet, PDF (163/847 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

Section 6 Bus Controller
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_W) selected by
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.
Inserted by Inserted by
wait count WAIT signal
T₁
T₂
T_W
T_W
T₃
φ
*
*
WAIT pin
Address bus
External address
AS
Read
access
RD
Data bus
Read data
Write
access
HWR, LWR
Data bus
Write data
Note: * Arrows indicate time of sampling of the WAIT pin.
Figure 6.13 Pin Wait Mode 1
Rev. 3.00 Mar 21, 2006 page 133 of 814
REJ09B0302-0300