Section 13 Bus State Controller (BSC)
SH7751 Group, SH7751R Group
Page 380 of 1128
R01UH0457EJ0301 Rev. 3.01
Sep 24, 2013
Bits 12 to 10—CAS-Before-RAS Refresh
RAS
Assertion Period (TRAS2–TRAS0):
When the
DRAM interface is set, these bits set the
RAS
assertion period in CAS-before-RAS refreshing.
When the synchronous DRAM interface is set, the bank active command is not issued for a period
set by TPC[2:0] and TRAS[2:0] bits after an auto-refresh command is issued.
Note: For setting values and the period during which no command is issued, see 23.3.3, Bus
Timing.
Bit 12: TRAS2
Bit 11: TRAS1
Bit 10: TRAS0
RAS
/DRAM
Assertion Time
Command Interval after
Synchronous DRAM
Refresh
0 0 0 2 4
+
TRC
(Initial
value)
1
3
5
+
TRC
1 0 4 6
+
TRC
1
5
7
+
TRC
1 0 0 6 8
+
TRC
1
7
9
+
TRC
1 0 8 10
+
TRC
1
9
11
+
TRC
Note: TRC (Bits 29 to 27): RAS precharge interval at end of refresh
Bit 9—Burst Enable (BE):
Specifies whether burst access is performed on DRAM interface. In
synchronous DRAM access, burst access is always performed regardless of the specification of
this bit. The DRAM transfer mode depends on EDOMODE.
BE EDOMODE 8/16/32/64-Bit
Transfer
32-Byte Transfer
0 0
Single
Single
1
Setting
prohibited
Setting prohibited
1 0
Single/fast
page
*
Fast page
1
EDO
EDO
Note:
*
In fast page mode, 32-bit or 64-bit transfer with a 16-bit bus, 64-bit transfer with a 32-bit
bus