SH7619_09 Datasheet, PDF (196/860 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7619 Series

Section 7 Bus State Controller (BSC)
7.5.4 Extension of Chip Select (CSn) Assertion Period
The number of cycles from CSn assertion to RD and WEn (BEn) assertion can be specified by
setting bits SW1 and SW0 in CSnWCR. The number of cycles from RD and WEn (BEn) negation
to CSn negation can be specified by setting bits HW1 and HW0. Therefore, a flexible interface to
an external device can be obtained. Figure 7.11 shows an example. A Th cycle and a Tf cycle are
added before and after a normal cycle, respectively. In these cycles, RD and WEn (BEn) are not
asserted, while other signals are asserted. The data output is prolonged to the Tf cycle, and this
prolongation is useful for devices with slow writing operations.
Th
T1
T2
Tf
CKIO
A25 to A0
CSn
RD/WR
RD
Read
D
Write
WEn(BEn)
D
BS
Figure 7.11 Example of Timing when CSn Assertion Period is Extended
Rev. 6.00 Jul. 15, 2009 Page 156 of 816
REJ09B0237-0600