HD64F2145 Datasheet, PDF (170/829 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

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 :$,7 pin, and the combination of program wait and the :$,7 pin.
Program Wait Mode: A specified number of wait states T_W can be inserted automatically
between the T₂ state and T₃ state when accessing the external address space always according to
the settings of the WC1 and WC0 bits in WSCR.
Pin Wait Mode: A specified number of wait states T_W can be inserted automatically between the
T₂ state and T₃ state when accessing the external address space always according to the settings of
the WC1 and WC0 bits. If the :$,7 pin is low at the falling edge of ø in the last T₂ or T_W state,
another T_W state is inserted. If the :$,7 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 T₂ state and T₃ state when accessing the external address space according to the
settings of the WC1 and WC0 bits if the :$,7 pin is low at the falling edge of ø in the last T₂
state. Even if the :$,7 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 :$,7 pin.
Figure 6.13 shows an example of wait state insertion timing in pin wait mode.
The settings after a reset are: 3-state access, 3 program wait insertion, and :$,7 pin input
disabled.
Rev. 2.0, 08/02, page 130 of 788