h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 205

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

6.4.5
When accessing external space, the MCU can extend the bus cycle by inserting one or more wait
states (T
using the WAIT pin, and a combination of the two.
Program Wait Mode
In program wait mode, the number of T
inserted between the T
Pin Wait Mode
In pin wait mode, the number of T
between the T
inserted until it goes high.
Pin wait mode is useful for inserting four or more wait states, or for changing the number of T
states for different external devices.
Pin Auto-Wait Mode
In pin auto-wait mode, if the WAIT pin is low at the fall of the system clock in the T
number of T
when external space is accessed. No additional T
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 6.7 shows an example of wait state insertion timing.
in the last T
W
). There are three ways of inserting wait states: program wait insertion, pin wait insertion
Wait Control
W
2
2
states specified by bits WC1 and WC0 are inserted between the T
or T
and T
W
state, another T
3
states when external space is accessed. If the WAIT pin is low at the fall of
2
and T
3
states when external space is accessed.
W
states specified by bits WC1 and WC0 are always inserted
W
state is inserted. If the WAIT pin is held low, T
W
states specified by bits WC1 and WC0 are always
W
states are inserted even if the WAIT pin
Rev. 4.00 Jun 06, 2006 page 151 of 1004
Section 6 Bus Controller
2
REJ09B0301-0400
and T
2
W
state, the
3
states are
states
W