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4.3 Bus Interface Registers
automatically by one cycle in DRAM access.
0: Not prolonged (initial value)
1: Prolonged
[Bit 10] Q4W (Q4 wait bit)
This bit indicates whether the Q4 cycle (CAS level is set to "H") is to be prolonged
automatically by one cycle in DRAM access. This bit is valid only while the DSAS bit (bit 9)
is set to "0".
0: Not prolonged (initial value)
1: Prolonged
[Bit 9] DSAS (Double/Single cas Access cycle Select bit)
This bit selects two-cycle CAS access (double CAS access) or one-cycle CAS access (single
CAS access) when high-speed page mode is used for DRAM access.
0: Double CAS access (initial value)
1: Single CAS access
[Bit 8] HYPR (HYPeR-page mode enable)
Set this bit to externally connect a DRAM with hyper-page mode supported.
This bit is valid only while the DSAS bit (bit 9) is set to "1".
0: Double/single CAS DRAM (initial value)
1: DRAM with hyper-page mode supported
[Bit 7] PAGE (PAGe Enable bit)
This bit indicates whether high-speed page mode is enabled.
0: Invalid (Only random access is used; this is the initial value.)
1: Valid (Access to a page specified in PGS3 to 0 is executed in high-speed page mode.)
[Bit 6] C/W (1CAS-2WE/2CAS/1WE select bit)
This bit indicates whether the 1CAS-2WE type memory interface or the 2CAS-1WE type
memory interface is to be used when using a bus width of 16 bits or more.
0: 1CAS-2WE interface (initial value)
1: 2CAS-1WE interface
[Bit 5] SLFR (SeLF Refresh bit)
When this bit is set to "1", the DRAM switches to self refresh mode.
Self refresh mode can be activated by setting this bit to "1" in either of the DMCR4 and
DMCR5 registers for areas 4 and 5.
This bit can be accessed with any timing, but sufficient time for RAS recovery time should be
set when releasing DRAM self refresh mode.
0: Self refresh mode is not applied (initial value).
1: Self refresh mode is applied.
[Bit 4] REFE (REFresh Enable bit)
This bit indicates whether the cyclic refresh operation is to be performed with the CAS
Before RAS (CBR) method. The refresh cycle can be executed for areas 4 and 5 by setting
this bit to "1" in either of the DMCR4 and DMCR5 registers and writing data to the STR bit in
the refresh control register (RFCR).