SH7263 Datasheet, PDF (383/1862 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7260 Series

Section 9 Bus State Controller (BSC)
(13) Low-Power SDRAM
The low-power SDRAM can be accessed using the same protocol as the normal SDRAM.
The differences between the low-power SDRAM and normal SDRAM are that partial refresh
takes place that puts only a part of the SDRAM in the self-refresh state during the self-refresh
function, and that power consumption is low during refresh under user conditions such as the
operating temperature. The partial refresh is effective in systems in which there is data in a work
area other than the specific area can be lost without severe repercussions.
The low-power SDRAM supports the extension mode register (EMRS) in addition to the mode
registers as the normal SDRAM. This LSI supports issuing of the EMRS command.
The EMRS command is issued according to the conditions specified in table below. For example,
if data H'0YYYYYYY is written to address H'FFFC5XX0 in longword, the commands are issued
to the CS3 space in the following sequence: PALL -> REF × 8 -> MRS -> EMRS. In this case, the
MRS and EMRS issue addresses are H'0000XX0 and H'YYYYYYY, respectively. If data
H'1YYYYYYY is written to address H'FFFC5XX0 in longword, the commands are issued to the
CS3 space in the following sequence: PALL -> MRS -> EMRS.
Table 9.19 Output Addresses when EMRS Command Is Issued
Command to be
Issued
CS2 MRS
CS3 MRS
CS2 MRS + EMRS
(with refresh)
CS3 MRS + EMRS
(with refresh)
CS2 MRS + EMRS
(without refresh)
CS3 MRS + EMRS
(without refresh)
Access
Address
Write
Access
Access Data Size
H'FFFC4XX0 H'******** 16 bits
H'FFFC5XX0 H'******** 16 bits
H'FFFC4XX0 H'0YYYYYYY 32 bits
H'FFFC5XX0 H'0YYYYYYY 32 bits
H'FFFC4XX0 H'1YYYYYYY 32 bits
H'FFFC5XX0 H'1YYYYYYY 32 bits
MRS
EMRS
Command Command
Issue Address Issue Address
H'0000XX0 ⎯
H'0000XX0 ⎯
H'0000XX0 H'YYYYYYY
H'0000XX0 H'YYYYYYY
H'0000XX0 H'YYYYYYY
H'0000XX0 H'YYYYYYY
Rev. 2.00 Mar. 14, 2008 Page 349 of 1824
REJ09B0290-0200