HD6413008VF25 Datasheet, PDF (179/688 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

6. Bus Controller
Pin Wait Insertion: Setting the WAITE bit in BCR to 1 enables wait insertion by means of the
WAIT pin. When external space is accessed in this state, a program wait is first inserted. If the
WAIT pin is low at the falling edge of φ in the last T₂ or T_W state, another T_W state is inserted. If
the WAIT pin is held low, T_W states are inserted until it goes high.
This is useful when inserting four or more T_W states, or when changing the number of T_W states for
different external devices.
The WAITE bit setting applies to all areas.
Figure 6.17 shows an example of the timing for insertion of one program wait state in 3-state
space.
Inserted
by program wait Inserted by WAIT pin
T1
T2
Tw
Tw
Tw
T3
φ
WAIT
Address bus
AS
Read access
RD
Data bus
Read data
Write access
HWR, LWR
Data bus
Write data
Note: indicates the timing of WAIT pin sampling.
Figure 6.17 Example of Wait State Insertion Timing
Rev.4.00 Aug. 20, 2007 Page 133 of 638
REJ09B0395-0400