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4.3 Bus Interface Registers
1: Add Q1 cycle
Bit 10: Q4W (Q4 Wait)
This bit specifies whether to add another Q4 cycle (RAS level high) for DRAM access
automatically. This bit is valid only when the DSAS bit (bit 9) is 0.
0: Do not add Q4 cycle (Initial value)
1: Add Q4 cycle
Bit 9: DSAS (Double/Single CAS Access Cycle Select)
When using high-speed page mode for DRAM access, this bit specifies two CAS access
cycles (double CAS access) or one CAS access cycle (single CAS access).
0: Double CAS access (Initial value)
1: Single CAS access
Bit 8: HYPR (Hyper Page Mode Enable)
This bit is used to connect an external DRAM device supporting hyper page mode.
This bit is valid only when the DSAS bit (bit 9) is 1.
0: Double/single CAS DRAM (Initial value)
1: DRAM supporting hyper page mode
Bit 7: PAGE (Page Enable)
This bit is used to enable high-speed page mode.
0: Disable high-speed page mode (for random access) (Initial value)
1: Enable high-speed page mode (high-speed page mode for access in the page specified
by PGS3 to PGS0)
Bit 6: C/W (1CAS-2WE/2CAS-1WE Select)
This bit specifies the 1CAS-2WE or 2CAS-1WE memory interface for using a 16-bit or wider
interface.
0: 1CAS-2WE interface (Initial value)
1: 2CAS-1WE interface
Bit 5: SLFR (Self Refresh)
Writing 1 into this bit changes DRAM to self-refresh mode.
Regardless of areas 4 and 5, self-refresh mode is activated when 1 is written into this bit in
DMCR4 or DMCR5.
This bit can be read or written at an arbitrary timing. When DRAM self-refresh mode is
released, however, reserve an adequate RAS recovery time.
0: Release self-refresh mode (Initial value)
1: Activate self-refresh mode
Bit 4: REFE (Refresh Enable)
This bit controls cyclic refresh of the CAS before RAS (CBR) system.
Regardless of areas 4 and 5, cyclic refresh is enabled when 1 is written into this bit in
DMCR4 or DMCR5 and also to the STR bit in the refresh control register (RFCR).
0: Disable refresh (Initial value)
1: Enable refresh (at the intervals specified by the refresh control register(RFCR))