Digi manual NS7520 Sdram interconnect, X32 Sdram configuration, X32 Sdram interconnect

S D R A M

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

1 1 2 N S 7 5 2 0 H a r d w a r e R e f e r e n c e , R e v . D 0 3 / 2 0 0 6