Section 6 Bus Controller (BSC)
Rev. 1.00 Mar. 12, 2008 Page 148 of 1178
REJ09B0403-0100
6.5.6 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
pin, and the combination of program wait and the
WAIT
pin.
(1) In Normal Extended Mode
(a) Program Wait Mode
A specified number of wait states T
W
are always inserted between the T
2
state and T
3
state when
accessing the external address space. The number of wait states T
W
is specified by the settings of
the WC1 and WC0 bits in WSCR (the WC11 and WC10 bits in WSCR2 for the 256-Kbyte
extended area).
(b) Pin Wait Mode
A specified number of wait states T
W
are always inserted between the T
2
state and T
3
state when
accessing the external address space. The number of wait states T
W
is specified by the settings of
the WC1 and WC0 bits. If the
WAIT
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
pin is held low, T
W
states are inserted until it goes high.
Pin wait mode 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.
(c)
Pin Auto-Wait Mode
A specified number of wait states T
W
are inserted between the T
2
state and T
3
state when accessing
the external address space if the
WAIT
pin is low at the falling edge of
φ
in the last T
2
state. The
number of wait states T
W
is specified by the settings of the WC1 and WC0 bits. Even if the
WAIT
pin is held low, T
W
states are inserted only up to the specified number of states.
Pin auto-wait mode enables the low-speed memory interface only by inputting the chip select
signal to the
WAIT
pin.
Figure 6.28 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
pin input
disabled.
Summary of Contents for H8S Family
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Page 70: ...Section 1 Overview Rev 1 00 Mar 12 2008 Page 22 of 1178 REJ09B0403 0100...
Page 108: ...Section 2 CPU Rev 1 00 Mar 12 2008 Page 60 of 1178 REJ09B0403 0100...
Page 116: ...Section 3 MCU Operating Modes Rev 1 00 Mar 12 2008 Page 68 of 1178 REJ09B0403 0100...
Page 152: ...Section 5 Interrupt Controller Rev 1 00 Mar 12 2008 Page 104 of 1178 REJ09B0403 0100...
Page 206: ...Section 6 Bus Controller BSC Rev 1 00 Mar 12 2008 Page 158 of 1178 REJ09B0403 0100...
Page 420: ...Section 9 14 Bit PWM Timer PWMX Rev 1 00 Mar 12 2008 Page 372 of 1178 REJ09B0403 0100...
Page 476: ...Section 12 Watchdog Timer WDT Rev 1 00 Mar 12 2008 Page 428 of 1178 REJ09B0403 0100...
Page 552: ...Section 14 CRC Operation Circuit CRC Rev 1 00 Mar 12 2008 Page 504 of 1178 REJ09B0403 0100...
Page 712: ...Section 18 I2 C Bus Interface IIC Rev 1 00 Mar 12 2008 Page 664 of 1178 REJ09B0403 0100...
Page 804: ...Section 19 LPC Interface LPC Rev 1 00 Mar 12 2008 Page 756 of 1178 REJ09B0403 0100...
Page 838: ...Section 20 Ethernet Controller EtherC Rev 1 00 Mar 12 2008 Page 790 of 1178 REJ09B0403 0100...
Page 964: ...Section 24 RAM Rev 1 00 Mar 12 2008 Page 916 of 1178 REJ09B0403 0100...
Page 1066: ...Section 25 Flash Memory Rev 1 00 Mar 12 2008 Page 1018 of 1178 REJ09B0403 0100...
Page 1098: ...Section 26 Boundary Scan JTAG Rev 1 00 Mar 12 2008 Page 1050 of 1178 REJ09B0403 0100...
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Page 1230: ...H8S 2472 Group H8S 2462 Group Hardware Manual...