Section 8 Bus State Controller (BSC)
Rev. 5.00 May 29, 2006 page 211 of 698
REJ09B0146-0500
8.5.4
Synchronous DRAM Interface
Synchronous DRAM Direct Connection
Since synchronous DRAM can be selected by the
CS
signal, physical space areas 2 and 3 can be
connected using
RAS
and other control signals in common. If the memory type bits (DRAMTP2
to 0) in BCR1 are set to 010, area 2 is ordinary memory space and area 3 is synchronous DRAM
space; if set to 011, areas 2 and 3 are both synchronous DRAM space. However, do not access to
the synchronous DRAM when clock ratio is I
φ
:B
φ
= 1:1.
With this LSI, burst length 1 burst read/single write mode is supported as the synchronous DRAM
operating mode. A data bus width of 16 or 32 bits can be selected. A 16-byte burst transfer is
performed in a cache fill/write-back cycle, and only one access is performed in a write-through
area write or a non-cacheable area read/write.
The control signals for direct connection of synchronous DRAM are
RASL
,
RASU
,
CASL
,
CASU
, RD/
WR
,
CS2
or
CS3
,
DQMUU
,
DQMUL
,
DQMLU
,
DQMLL
, and CKE. All the signals
other than
CS2
and
CS3
are common to all areas, and signals other than CKE are valid and fetched
to the synchronous DRAM only when
CS2
or
CS3
is asserted. Synchronous DRAM can therefore
be connected in parallel to a number of areas. CKE is negated (low) only when self-refreshing is
performed, and is always asserted (high) at other times.
In the refresh cycle and mode-register write cycle,
RASU
and
RASL
or
CASU
and
CASL
are
output.
Commands for synchronous DRAM are specified by
RASL
,
RASU
,
CASL
,
CASU
, RD/
WR
, and
special address signals. The commands are NOP, auto-refresh (REF), self-refresh (SELF),
precharge all banks (PALL), row address strobe bank active (ACTV), read (READ), read with
precharge (READA), write (WRIT), write with precharge (WRITA), and mode register write
(MRS).
Byte specification is performed by
DQMUU
,
DQMUL
,
DQMLU
, and
DQMLL
. A read/write is
performed for the byte for which the corresponding DQM is low. In big-endian mode,
DQMUU
specifies an access to address 4n, and
DQMLL
specifies an access to address 4n + 3. In little-
endian mode,
DQMUU
specifies an access to address 4n + 3, and
DQMLL
specifies an access to
address 4n.
Figures 8.11 shows examples of the connection of two 1M
×
16-bit
×
4-bank synchronous
DRAMs and figure 8.12 shows one 1M
×
16-bit
×
4-bank synchronous DRAM, respectively.
Summary of Contents for SH7706 Series
Page 8: ...Rev 5 00 May 29 2006 page viii of xlviii ...
Page 160: ...Section 5 Cache Rev 5 00 May 29 2006 page 112 of 698 REJ09B0146 0500 ...
Page 370: ...Section 11 Watchdog Timer WDT Rev 5 00 May 29 2006 page 322 of 698 REJ09B0146 0500 ...
Page 554: ...Section 17 Pin Function Controller PFC Rev 5 00 May 29 2006 page 506 of 698 REJ09B0146 0500 ...
Page 576: ...Section 18 I O Ports Rev 5 00 May 29 2006 page 528 of 698 REJ09B0146 0500 ...
Page 746: ...Index Rev 5 00 May 29 2006 page 698 of 698 REJ09B0146 0500 ...
Page 749: ...SH7706 Group Hardware Manual ...