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NS7520 Hardware Reference, Rev. D 03/2006
NS7520 SDRAM interconnect
The NS7520 can interconnect to standard 16Mb and 64Mb SDRAM components, using
x32, x16, and x8 SDRAM configuration.
You can use 128Mb components in the x32 configuration, but not in the x8 or x16
configurations. The NS7520 SDRAM controller does not support SDRAM with more than
8 CAS (column addressing).
x32 SDRAM configuration
Table 42 shows the interconnect between the NS7520 and SDRAM when SDRAM is used
in an x32 configuration. This table shows two ways of constructing an x32 SDRAM
configuration:
Using two x16 SDARM components (referred to as Device 1 and Device 2)
Using one x32 SDRAM component
In the 2Mx32 SDRAM configuration, bank selects BA0 and BA1 are not connected in
numerical order. The order is reversed so BA0 can be the same for the 4Mx32
configuration, and only BA1 needs to be swapped to upgrade.
2x16M SDRAM signal components 1x32 SDRAM component
NS7520 signal 16 Mb (1Mx16) 64Mb (4Mx16) 64Mb (2Mx32) 128Mb (4Mx32)
CS/RAS_ CS[4:0]_ CS[4:0]_ CS[4:0]_ CS[4:0]_
CAS3_ RAS_ RAS_ RAS_ RAS_
CAS2_ CAS_ CAS_ CAS_ CAS_
CAS1_ WE_ WE_ WE_ WE_
CAS0_A10/AP A10/AP A10/AP A10/AP A10/AP
BE3_ UDQM_ - Device 1 UDQM_ - Device 1 DQM3 DQM3
BE2_ LDQM_ - Device 1 LDQM_ - Device 1 DQM2 DQM2
BE1_ UDQM_ - Device 2 UDQM_ - Device 2 DQM1 DQM1
BE0_ LDQM_ - Device 2 LDQM_ - Device 2 DQM0 DQM0
Table 42: x32 SDRAM interconnect