H8S2245 datasheet(206/818 Pages) RENESAS

tên linh kiện	H8S2245

Giải thích chi tiết về linh kiện	Renesas 16-Bit Single-Chip Microcomputer H8S Family / H8S/2200 Series

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Section 6 Bus Controller

Rev.3.00 Mar. 26, 2007 Page 164 of 772

REJ09B0355-0300

6.5.5

Wait Control

When accessing external space, the H8S/2245 Group can extend the bus cycle by inserting one or

more wait states (T

w). There are two ways of inserting wait states: (1) program wait insertion and

(2) pin wait insertion using the

WAIT pin.

(1) Program Wait Insertion

From 0 to 3 wait states can be inserted automatically between the T

2 state and T3 state on an

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

(2) Pin Wait Insertion Using

WAIT

WAIT Pin

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 T

2 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 T

w states, or when changing the number of Tw states for

different external devices.

The WAITE bit setting applies to all areas.

H8S2245 bảng dữ liệu(PDF) 206 Page - Renesas Technology Corp