SH7606 Datasheet, PDF (216/532 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family / SH7606 Series

Section 7 Bus State Controller (BSC)
7.5.8 Wait between Access Cycles
Data output in the previous cycle may conflict with that in the next cycle because the buffer-off
timing of devices with slow access speed cannot be operated to satisfy the higher operating
frequency of LSIs. As a result of these conflict, the reliability of the device is low and
malfunctions may occur. This LSI has a function that avoids data conflicts by inserting wait cycles
between consecutive access cycles.
The number of wait cycles between access cycles can be set by bits IWW1 and IWW0, bits
IWRWD1 and IWRWD0, bits IWRWS1 and IWRWS0, bits IWRRD1 and IWRRD0, and bits
IWRRS1 and IWRRS0 in CSnBCR. The conditions for setting the wait cycles between access
cycles (idle cycles) are shown below.
1. Consecutive accesses are write-read or write-write
2. Consecutive accesses are read-write for different areas
3. Consecutive accesses are read-write for the same area
4. Consecutive accesses are read-read for different areas
5. Consecutive accesses are read-read for the same area
7.5.9 Others
Reset: The bus state controller (BSC) can be initialized completely only by a power-on reset. At
power-on reset, all signals are negated and output buffers are turned off regardless of the bus cycle
state. All control registers are initialized. In standby mode and sleep mode, control registers of the
BSC are not initialized.
Some flash memories may stipulate a minimum time from reset release to the first access. To
ensure this minimum time, the BSC supports a 5-bit counter (RWTCNT). At a power-on reset, the
RWTCNT contents are cleared to 0. After a power-on reset, RWTCNT is counted up in
synchronization with the CKIO signal and an external access will not be generated until
RWTCNT is counted up to H'007F.
Access from the Site of the LSI Internal Bus Master: There are three types of LSI internal
buses: a cache bus, internal bus, and peripheral bus. The CPU and cache memory are connected to
the cache bus. The BSC is connected to the internal bus. Low-speed peripheral modules are
connected to the peripheral bus. Internal memory other than the cache memory and debugging
modules such as the UBC are connected to both the cache bus and internal bus. Access from the
cache bus to the internal bus is enabled but access from the internal bus to the cache bus is
disabled.
Rev. 4.00 Sep. 13, 2007 Page 190 of 502
REJ09B0239-0400