Section 6 Bus Controller
Rev. 3.00 Jan 25, 2006 page 133 of 872
REJ09B0286-0300
6.5.4
Wait Control
When accessing the external address space, this LSI can extend the bus cycle by inserting one or
more wait states (T
W
). There are three ways of inserting wait states: Program wait insertion, pin
wait insertion using the
WAIT
/
CPWAIT
pin, and the combination of program wait and the
WAIT
/
CPWAIT
pin.
Program Wait Mode:
A specified number of wait states T
W
can be inserted automatically
between the T
2
state and T
3
state when accessing the external address space always according to
the settings of the WC1 and WC0 bits in WSCR (the WC11 and WC10 bits in WSCR2 for the
256-kbyte expansion area, and the WC21 and WC20 bits in WSCR2 for the CP expansion area).
Pin Wait Mode:
A specified number of wait states T
W
can be inserted automatically between the
T
2
state and T
3
state when accessing the external address space always according to the settings of
the WC1 and WC0 bits (the WC21 and WC20 bits for the CP expansion area). If the
WAIT
/
CPWAIT
pin is low at the falling edge of
φ
in the last T
2
or T
W
state, another T
W
state is
inserted. If the
WAIT
/
CPWAIT
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 to
be inserted for each external device.
Pin Auto-Wait Mode:
A specified number of wait states T
W
can be inserted automatically
between the T
2
state and T
3
state when accessing the external address space according to the
settings of the WC1 and WC0 bits (the WC21 and WC20 bits for the CP expansion area) if the
WAIT
/
CPWAIT
pin is low at the falling edge of
φ
in the last T
2
state. Even if the
WAIT
/
CPWAIT
pin is held low, T
W
states can be inserted only up to the specified number of states.
This function enables the low-speed memory interface only by inputting the chip select signal to
the
WAIT
/
CPWAIT
pin.
Figure 6.13 shows an example of wait state insertion timing in pin wait mode.
The settings after a reset are: 3-state access, 3 program wait insertion, and
WAIT
/
CPWAIT
pin
input disabled.
Summary of Contents for H8S/2158
Page 10: ...Rev 3 00 Jan 25 2006 page viii of lii...
Page 36: ...Rev 3 00 Jan 25 2006 page xxxiv of lii B Product Lineup 863 C Package Dimensions 864 Index 865...
Page 47: ...Rev 3 00 Jan 25 2006 page xlv of lii Appendix Figure C 1 Package Dimensions TBP 112A 864...
Page 54: ...Rev 3 00 Jan 25 2006 page lii of lii...
Page 70: ...Section 1 Overview Rev 3 00 Jan 25 2006 page 16 of 872 REJ09B0286 0300...
Page 118: ...Section 3 MCU Operating Modes Rev 3 00 Jan 25 2006 page 64 of 872 REJ09B0286 0300...
Page 126: ...Section 4 Exception Handling Rev 3 00 Jan 25 2006 page 72 of 872 REJ09B0286 0300...
Page 198: ...Section 6 Bus Controller Rev 3 00 Jan 25 2006 page 144 of 872 REJ09B0286 0300...
Page 326: ...Section 10 8 Bit PWM Timer PWM Rev 3 00 Jan 25 2006 page 272 of 872 REJ09B0286 0300...
Page 440: ...Section 15 Watchdog Timer WDT Rev 3 00 Jan 25 2006 page 386 of 872 REJ09B0286 0300...
Page 606: ...Section 17 I 2 C Bus Interface IIC Rev 3 00 Jan 25 2006 page 552 of 872 REJ09B0286 0300...
Page 742: ...Section 19 Multimedia Card Interface MCIF Rev 3 00 Jan 25 2006 page 688 of 872 REJ09B0286 0300...
Page 750: ...Section 21 D A Converter Rev 3 00 Jan 25 2006 page 696 of 872 REJ09B0286 0300...
Page 768: ...Section 22 A D Converter Rev 3 00 Jan 25 2006 page 714 of 872 REJ09B0286 0300...
Page 770: ...Section 23 RAM Rev 3 00 Jan 25 2006 page 716 of 872 REJ09B0286 0300...
Page 824: ...Section 26 Clock Pulse Generator Rev 3 00 Jan 25 2006 page 770 of 872 REJ09B0286 0300...
Page 844: ...Section 27 Power Down Modes Rev 3 00 Jan 25 2006 page 790 of 872 REJ09B0286 0300...
Page 878: ...Section 28 List of Registers Rev 3 00 Jan 25 2006 page 824 of 872 REJ09B0286 0300...
Page 926: ...Index Rev 3 00 Jan 25 2006 page 872 of 872 REJ09B0286 0300...