BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
114
Section 6: DRAM
Document
1250_1125-UM100CB-R
is an alternative that uses chip select interleaving to (on average) increase the number of active
banks. Notice the chip select ranges are now the same for both selects.
Figure 18: Example 1GB with two chip selects interleaved on one channel
On the BCM1250 there is a higher performance possibility. Rather than putting both physical banks on the
same channel one can be put on each channel. This doubles the number of data bits in use (since the controller
can run both channels in parallel), allowing twice the peak bandwidth.
Channel 0, chip select 0
bank2_map
bank1_map
bank0_map
Expansion space
Physical Address
(used by CPU and DMA)
MC Address Space
(only used for MC configuration)
00_0000_0000
00_1000_0000
00_8000_0000
00_9000_0000
00_A000_0000
00_C000_0000
00_D000_0000
01_0000_0000
80_0000_0000
FF_FFFF_FFFF
First SDRAM
Peripherals
Second SDRAM
Third SDRAM
Reserved
Fourth SDRAM
Peripherals/L2 mgmt
SDRAM Expansion
HT
This range cannot
be accessed
bank3_map
direct map
cs0_start=00_00 cs0_end=00_40
Channel 0, chip select 1
cs1_start=00_00 cs1_end=00_40
cs_interleave=bit7, cs_mode=mixed