13.3.15 Cooperation Between Master And Slave - Hitachi SH7750 Hardware Manual

Area 2 synchronous DRAM mode register settings should be made by the master mode device. Set
partial-sharing master mode (by setting the PSHR bit to 1 in BCR1) after completion of the area 3
synchronous DRAM mode register settings.
In partial-sharing master mode, DMA transfer should not be performed on area 2, and the
DMAC's DDT mode should not be used.

13.3.15 Cooperation between Master and Slave

To enable system resources to be controlled in a harmonious fashion by master and slave, their
respective roles must be clearly defined. Before DRAM or synchronous DRAM is used,
initialization operations must be carried out. Responsibility must also be assigned when a standby
operation is performed to implement the power-down state.
The design of the SH7750 Series provides for all control, including initialization, refreshing, and
standby control, to be carried out by the master mode device. In a dual-processor configuration
using direct master/slave connection, all processing except direct access to memory is handled by
the master. In a combination of master mode and partial-sharing master mode, the partial-sharing
master mode processor performs initialization, refreshing, and standby control for the areas
connected to it, with the exception of area 2, while the master performs initialization of the
memory connected to it.
If the SH7750 Series is specified as the master in a power-on reset, it will not accept bus requests
from the slave until the BREQ enable bit (BCR1.BREQEN) is set to 1.
To ensure that the slave processor does not access memory requiring initialization before use, such
as DRAM and synchronous DRAM, until initialization is completed, write 1 to the BREQ enable
bit after initialization ends.
Before setting self-refresh mode in standby mode, etc., write 0 to the BREQ enable bit to
invalidate the BREQ signal from the slave. Write 1 to the BREQ enable bit only after the master
has performed the necessary processing (refresh settings, etc.) for exiting self-refresh mode.
Rev. 6.0, 07/02, page 486 of 986