User Manual
BCM1250/BCM1125/BCM1125H
10/21/02
B r o a d c o m C o r p o r a t i o n
Document
1250_1125-UM100CB-R
Section 6: DRAM
Page
119
The previous examples show interleaving between the banks within a device. It is also possible to use
interleave between chip selects on a channel. This is done by setting an appropriate mode in the
mc_config
register. If there are two chip selects available on a channel (i.e. there are two physical banks of memory of
the same size) then the mixed_cs mode can be used to allow them to be interleaved. When this mode is set
the
mc_cs_interleave
register can have a single bit set to program which bit of the address is used to switch
between chip selects.
gives an example of this, the same 128 byte interleave is done between banks
on the same device, but the upper row and column bits have been moved to allow for switching between the
devices on the channel using bit [9].
If there are four physical banks of memory then the interleave_cs mode can be used to allow a full interleave
between the physical banks. This is shown in
Table 64: Example for 128 MByte CS Region with 4K Rows, 1K Columns, 128 Byte Interleave
Row Address Bits [26:15], Column Address Bits [14:9,6:5,4:3], Bank Address Bits [8:7]
Row
00000000_00000111_11111111_10000000_00000000
Column
00000000_00000000_00000000_01111110_01100000
Bank
00000000_00000000_00000000_00000001_10000000
Table 65: Example for 256 MByte Region with 4K Rows, 1K Columns, two CS, and 128 Byte Interleave
Row Address Bits [27:16], Column Address Bits [15:10,6:5,4:3], Bank Address Bits [8:7], mixed_cs
Selected by Bit [9]
Row
00000000_00001111_11111111_00000000_00000000
Column
00000000_00000000_00000000_11111100_01100000
Bank
00000000_00000000_00000000_00000001_10000000
CS Interleave
00000000_00000000_00000000_00000010_00000000
Table 66: Example for 512 MByte Region with 4K Rows, 1K Columns, four CS, and 128 Byte Interleave
Row Address Bits [27:17], Column Address Bits [16:11,6:5,4:3], Bank Address Bits [8:7],
Interleaved_cs Selected by Bit [10:9]
Row
00000000_00011111_11111110_00000000_00000000
Column
00000000_00000000_00000001_11111000_01100000
Bank
00000000_00000000_00000000_00000001_10000000
CS Interleave
00000000_00000000_00000000_00000110_00000000