HD6432351 datasheet(193/1025 Pages) RENESAS

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Section 6 Bus Controller

Rev. 3.00 Sep 15, 2006 page 159 of 988

REJ09B0330-0300

6.4.5

Wait Control

When accessing external space, the H8S/2350 Group can extend the bus cycle by inserting one or

more wait states (Tw). There are two ways of inserting wait states: program wait insertion and pin

wait insertion using the

WAIT pin.

• Program Wait Insertion

From 0 to 3 wait states can be inserted automatically between the T2 state and T3 state on an

individual area basis in 3-state access space, according to the settings of WCRH and WCRL.

• Pin Wait Insertion

Setting the WAITE bit in BCRL to 1 enables wait insertion by means of the

WAIT pin.

Program wait insertion is first carried out according to the settings in WCRH and WCRL.

Then, if the

WAIT pin is low at the falling edge of φ in the last T2 or Tw state, a Tw 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 Tw states, or when changing the number of Tw states

for different external devices.

The WAITE bit setting applies to all areas.

HD6432351 bảng dữ liệu(PDF) 193 Page - Renesas Technology Corp