HD6417320 RENESAS [Renesas Technology Corp], HD6417320 Datasheet - Page 465

• Manufacturer Part Number: HD6417320
• Description: Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 9
Bus State Controller (BSC)
correctly, the slave device must be designed to release the bus mastership within the refresh
interval time. To achieve this, the LSI instructs the REFOUT pin to request the bus mastership
while the SDRAM waits for the refresh. The LSI asserts the REFOUT pin until the bus mastership
is received. If the slave releases the bus, the LSI acquires the bus mastership to execute the
SDRAM refresh.
The bus release by the BREQ and BACK signal handshaking requires some overhead. If the slave
has many tasks, multiple bus cycles should be executed in a bus mastership acquisition. Reducing
the cycles required for master to slave bus mastership transitions streamlines the system design.
CKIO
BREQ
BACK
A25 to A0
D31 to D0
CSn
Other bus
control signals
Figure 9.45
Bus Arbitration Timing
Rev. 3.00 Jan. 18, 2008 Page 403 of 1458
REJ09B0033-0300