Architecture
381
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
14.2.5 Address Mapping
The memory controller views the DDR2/mDDR SDRAM device as one continuous block of memory. The
memory controller receives memory access requests with a 32-bit logical address, and it uses the logical
address to generate a row, column, and bank address for accessing the DDR2/mDDR SDRAM device.
The memory controller supports two address mapping schemes: normal address mapping and special
address mapping. Special address mapping is typically used only with mDDR devices using partial array
self-refresh.
When the internal bank position (IBANKPOS) bit in the SDRAM configuration register (SDCR) is cleared,
the memory controller operates with normal address mapping. In this case, the number of column and
bank address bits is determined by the IBANK and PAGESIZE fields in SDCR. The number of row
address bits is determined by the number of valid address pins for the device and does not need to be set
in a register.
When IBANKPOS is set to 1, the memory controller operates with special address mapping. In this case,
the number of column, row, and bank address bits is determined by the PAGESIZE, ROWSIZE, and
IBANK fields. The ROWSIZE field is in the SDRAM configuration register 2 (SDCR2). See
for a
descriptions of these bit fields.
Table 14-4. Configuration Register Fields for Address Mapping
Bit Field
Bit Value
Bit Description
IBANK
Defines the number of internal banks in the external DDR2/mDDR memory.
0
1 bank
1h
2 banks
2h
4 banks
3h
8 banks
PAGESIZE
Defines the page size of each page in the external DDR2/mDDR memory.
0
256 words (requires 8 column address bits)
1h
512 words (requires 9 column address bits)
2h
1024 words (requires 10 column address bits)
3h
2048 words (requires 11 column address bits)
ROWSIZE
Defines the row size of each row in the external DDR2/mDDR memory
0
512 (requires 9 row address bits)
1h
1024 (requires 10 row address bits)
2h
2048 (requires 11 row address bits)
3h
4096 (requires 12 row address bits)
4h
8192 (requires 13 row address bits)
5h
16384 (requires 14 row address bits)