SH7205 Datasheet, PDF (338/1904 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7200 Series

Section 10 Bus State Controller (BSC)
4. Tn1 to Tnm (CS Delay Cycle)
These are the cycles between the wait end cycle and when CSn is negated (high level). The
negation timing can be controlled using write data output delay cycles. The number of cycles
is counted beginning from the wait end cycle. In write access or if the number of CS delay
cycles during a read is other than 0 or 1, the succeeding bus access can start from the cycle
following the CS delay cycle end. If the number of CS delay cycles is 0 or 1 in read access, the
succeeding bus access can start after the end of the read data sample cycle (see below).
5. Trd (Read Data Sample Cycle)
This is the sample cycle for read data.
(2) Page Access
Page read and write operation is employed for bus accesses for which page access can be used if
page write access enable (PWENB = 1) and page read access enable (PRENB = 1) have been
selected. Page access is used in the following cases.
1. CPU cache replace (cache filling and write-back). Each time a transfer occurs, the address is
incremented by the number of transferred bytes.
2. When longword (32-bit) access to an 8-bit or 16-bit external data bus has been performed.
3. When word (16-bit) access to an 8-bit external data bus has been performed.
Figure 10.4 shows the basic operation of the external bus control signals for page read operation,
and figure 10.5 shows the basic operation of these signals for page write operation. If the single
page access bit boundary setting made by the PBCNT bits in the mode register is smaller than the
cache line size, a single cache replacement will trigger multiple page accesses. When the address
exceeds the page boundary, page access stops once (the CSn signal is negated) and starts again. If
the PBCNT bit setting is not smaller than the cache line size, a cache replacement is processed in a
single page access.
Rev. 1.00 Mar. 25, 2008 Page 306 of 1868
REJ09B0372-0100