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II CORE BLOCK: BCU (Bus Control Unit)
B-II-4-24 EPSON S1C33L03 FUNCTION PART
DRAM Direct Interface
Outline of DRAM Interface
The BCU incorporates a DRAM direct interface that allows DRAM to be connected directly to areas 8 and 7 or
areas 14 and 13. This interface supports the 2CAS method, so that column addresses can be set at between 8 and 11
bits. In addition, this interface supports a fast-page or an EDO-page mode (EDO DRAM directly connectable to
areas) as well as random cycles. The refresh method (CAS-before-RAS refresh or self-refresh) and timing
conditions (e.g., number of RAS/CAS cycles and number of precharge cycles) can be programmed using a control
bit.
When selecting areas 8 and 7 or areas 14 and 13 to be used for DRAM, it depends on chip-enable settings using
CEFUNC (D9) / DRAM timing set-up register (0x48130).
CEFUNC = "00": DRAM can be connected to areas 8 and 7 (default)
#CE8 and #CE7 function as #RAS0 and #RAS1, respectively.
CEFUNC ≠ "00": DRAM can be connected to areas 14 and 13.
#CE14 and #CE13 function as #RAS2 and #RAS3, respectively.
Figure 4.27 shows a sample DRAM connection. Table 4.15 and Table 4.16 show examples of connectable DRAMs
and typical configurations.
A[9:1]
D[15:0]
#RD
#RASx(#CEx)*
#HCAS
#LCAS
#WE
S1C33
A[8:0]
I/O[15:0]
#OE
#RAS
#HCAS
#LCAS
#WE
4M DRAM
(256K x 16)
∗ x: 14, 13, 8 or 7
Figure 4.27 Sample DRAM Connection
Table 4.15 Connectable DRAM Example
DRAM
Number of
devices
Number of
Row bits
Number of
Column bits
Memory size
1M (64K x 16) 1 8 8 128K bytes
4M (256K x 16) 1 9 9 512K bytes
16M (1M x 16) 1 12 8 2M bytes
Table 4.16 DRAM Configuration Example (areas 7 and 8 only)
Area 7 Area 8 Total memory size
1 I/O DRAM (1M) 1M bits (128K bytes)
2 I/O DRAM (4M) 4M bits (512K bytes)
3 I/O DRAM (16M) 16M bits (2M bytes)
4 DRAM (1M) DRAM (1M) 2M bits (256K bytes)
5 DRAM (4M) DRAM (4M) 8M bits (1M bytes)
6 DRAM (16M) DRAM (16M) 32M bits (4M bytes)
Also, the S1C33L03 provides an SDRAM direct interface. Refer to "VI SDRAM Controller Block" for details.