R_SDRAM_CONFIG help document

General

The number of column, row and bank address bits is provided by the chip manufacturer normaly in the chip datasheet.

If both SDRAM groups are used, the chip configuration of these groups must be identical.

16bit Memory Configuration

Wide module mode (31-30)

Wide module mode is only used in 64 bit configuration, therefore both these bits should be 0.

Row address shift (29-27;26-24)

This value shows how many steps the row address in shifted. The register value should be N-8.

SDRAM bus width (23)

Set to 16 bit, that is 0.

Type (22;21)

Does the chip(s) have two or four banks? 2 banks is a 0. 4 banks is a 1.

Group select (20-16)

Selects which address bit that will be used to select between the groups. If only group 0 is used this fileld should have the value 0. If only group 1 is used this field should have the value 1. If both groups are used this field should have the value M+2 (2 banks) and M+3 (4 banks).

Cas address range (15-13;7-5)

This field selects how many address bits that are used for the column address. This value should be N-8.

Bank select

Selects which address bit that is used to select between bank 0/1. This field should have the value M+1.

Figure 1. 16bit Memory Configuration

32bit Memory Configuration

Wide module mode (31-30)

Wide module mode is only used in 64 bit configuration, therefore both these bits should be 0.

Row address shift (29-27;26-24)

This value shows how many steps the row address in shifted. The register value should be N-9.

SDRAM bus width (23)

Set to 32 bit, that is 1.

Type (22;21)

Does the chip(s) have two or four banks? 2 banks is a 0. 4 banks is a 1.

Group select (20-16)

Selects which address bit that will be used to select between the groups. If only group 0 is used this fileld should have the value 0. If only group 1 is used this field should have the value 1. If both groups are used this field should have the value M+2 (2 banks) and M+3 (4 banks).

Cas address range (15-13;7-5)

This field selects how many address bits that are used for the column address. This value should be N-8.

Bank select

Selects which address bit that is used to select between bank 0/1. This field should have the value M+1.

Figure 2. 32bit Memory Configuration

64bit Memory Configuration

Wide module mode (31-30)

Wide module mode should be enabled in this configuration, both bits should be 1.

Row address shift (29-27;26-24)

This value shows how many steps the row address in shifted. The register value should be N-8.

SDRAM bus width (23)

Set to 32 bit, that is 1.

Type (22;21)

Does the chip(s) have two or four banks? 2 banks is a 0. 4 banks is a 1.

Group select (20-16)

Selects which address bit that will be used to select between the groups. If only group 0 is used this fileld should have the value 0. If only group 1 is used this field should have the value 1. If both groups are used this field should have the value M+2 (2 banks) and M+3 (4 banks).

Cas address range (15-13;7-5)

This field selects how many address bits that are used for the column address. This value should be N-7. The VMM bit should be included in the cas address range.

Bank select

Selects which address bit that is used to select between bank 0/1. This field should have the value M+1.

Figure 3. 64bit Memory Configuration

Automatic calculation of the R_SDRAM_CONFIG value