SH7750_08 Datasheet, PDF (19/1162 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

Item
Page
13.3.4 DRAM Interface 463
Refresh Timing:
• Self-Refresh
Revision (See Manual for Details)
Description deleted
After the self-refresh is cleared, the refresh controller
immediately generates a refresh request. The RAS precharge
time immediately after the end of the self-refreshing can be set
by bits TRC2–TRC0 in MCR.
13.3.5 Synchronous 465
DRAM Interface
CAS-before-RAS refreshing is performed in normal operation,
in sleep mode, and in the case of a manual reset.
Description amended
With this LSI, burst read/burst write mode is supported as the
synchronous DRAM operating mode. The data bus width is 32
or 64 bits, and the SZ size bits in MCR must be set to 00 or 11.
The burst enable bit (BE) in MCR is ignored, a 32-byte burst
transfer is performed in a cache fill/copy-back cycle, and in a
write-through area write or a non-cacheable area read/write,
32-byte data is read even in a single read in order to access
synchronous DRAM with a burst read/write access. 32-byte
data transfer is also performed in a single write, but DQMn is
not asserted when unnecessary data is transferred. For details
on the burst length, see section 13.2.10, Synchronous DRAM
Mode Register (SDMR), and Power-On Sequence in section
13.3.5, Synchronous DRAM Interface. The SH7750R Group
supports burst read and burst write operations with a burst
length of 4 as a synchronous DRAM operating mode when
using a 32-bit data bus. The burst enable (BE) bit in MCR is
ignored, and a 32-byte burst transfer is performed in a cache fill
or copy-back cycle. In write-through area write operations and
non-cacheable area read or write operations, 16 bytes of data
is read even in a single read because burst read or write
accesses to synchronous DRAM use a burst length of 4.
Sixteen bytes of data is transferred in the case of a single write
also, but DQMn is not asserted when unnecessary data is
transferred.
For changing the burst length (a function only available in the
SH7750R) for a 32-bit bus, see Notes on Changing the Burst
Length (SH7750R Only) in section 13.3.5, Synchronous DRAM
Interface.
Rev.7.00 Oct. 10, 2008 Page xix of lxxxiv
REJ09B0366-0700