SH7011 Datasheet, PDF (96/292 Pages) Renesas Technology Corp – CMOS single-chip microprocessors

IW31 and IW30 specify the number of idle cycles required after a CS3 space read either to read
other external spaces, or for this LSI, to do write accesses. In the same manner, IW21 and IW20
specify the number of idle cycles after a CS2 space read, IW11 and IW10, the number after a CS1
space read, and IW01 and IW00, the number after a CS0 space read.
0 to 3 cycles can be specified for CS space.
7.4.2 Simplification of Bus Cycle Start Detection
For consecutive accesses of the same CS space, waits are inserted so that the number of idle cycles
designated by the CW3 to CW0 bits of the BCR2 occur. However, for write cycles after reads, the
number of idle cycles inserted will be the larger of the two values defined by the IW and CW bits.
When idle cycles already exist between access cycles, waits are not inserted. Figure 7.8 shows an
example. A continuous access idle is specified for CSn space, and CSn space is consecutively
write accessed.
T₁
T₂
T_idle
T₁
T₂
CK
Address
CSn
RD
WRx
Data
CSn space access
Idle cycle
CSn space access
Figure 7.8 Same Space Consecutive Access Idle Cycle Insertion Example
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