3.3.27. Chip Configuration Registers

The chip_cfg<n> Register characteristics are:

Purpose

Each register sets the:

  • address decode for chip select <n>

  • bank, row, column organization of the memory device that connects to chip select <n>.

Usage constraints
  • Only accessible in Config or Low_power state.

  • The number of registers implemented is equal to the number of chip selects that a configured controller supports.

Configurations

Available in all configurations of the DDR2 DMC.

Attributes

See the register summary in Table 3.1.

Figure 3.34 shows the chip_cfg<n> Register bit assignments.

Figure 3.34. chip_cfg<n> Registers bit assignments

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Table 3.28 shows the chip_cfg<n> Register bit assignments.

Table 3.28. chip_cfg<n> Registers bit assignments

BitsNameFunction
[31:17]-Read undefined, write as zero.

[16]

brc_n_rbc<n>

Selects the memory organization as decoded from the AXI address:

0 = Row, Bank, Column (RBC) organization

1 = Bank, Row, Column (BRC) organization.

[15:8]address_match<n>The controller applies the address_mask<n> field to the AXI address bits, [31:24], that is awaddr[31:24] or araddr[31:24]. The controller compares the result against this field and if a match occurs then it selects memory device <n>. See Formatting from AXI address channels.

[7:0]

address_mask<n>

Controls which AXI address bits [31:24] the DDR2 DMC compares when it receives an AXI transfer:

Bit [x] = 0

DDR2 DMC excludes AXI address bit [24+x] from the comparison

Bit [x] = 1

DDR2 DMC includes AXI address bit [24+x] in the comparison.


Note

If a configured controller supports two or more memory devices then you must take care to ensure that for all AXI addresses, you program the various address_match and address_mask fields so that the controller can only assert a single memory chip select. Otherwise, Unpredictable behavior might occur.

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