Integrated Functions (Continued)
4.3.1 Memory Array Configuration
component banks. Component bank selection is done
through the bank address (BA) lines.
The memory controller supports up to two 64-bit, 168-pin
unbuffered SDRAM modules (DIMM). Each DIMM
receives a unique set of RAS, CAS, WE, and CKE lines.
Each DIMM can have one or two 64-bit DIMM banks.
Each DIMM bank is selected by a unique chip select (CS).
There are four chip select signals to choose between a
total of four DIMM banks. Each DIMM bank also receives
a unique SDCLK. Each DIMM bank can have two or four
For example, 16 Mb SDRAMS have two component
banks and 64 Mb SDRAMs have two or four component
banks. For single DIMM bank modules, the memory con-
troller can support two DIMMS with a maximum of eight
component banks. For dual DIMM bank modules, the
memory controller can support two DIMMs with a maxi-
mum of 16 component banks. Up to 16 banks can be
open at the same time.
DIMM 0
Bank 0
Bank 1
MA[12:0]
BA[1:0]
MD[63:0]
DQM[7:0]
RASA#
CASA#
WEA#
A[12:0]
BA[1:0]
MD[63:0]
DQM[7:0]
RAS#
A[12:0]
BA[1:0]
MD[63:0]
DQM[7:0]
RAS#
CAS#
WE#
CAS#
WE#
CS0#
S0#, S2#
CS1#
CKEA
S1#, S3#
CKE1
CKE0
SDCLK0
SDCLK1
CK0, CK2
CK1, CK3
Geode™ GXm
Processor
DIMM 1
Bank 0
Bank 1
A[12:0]
BA[1:0]
MD[63:0]
DQM[7:0]
RAS#
A[12:0]
BA[1:0]
MD[63:0]
DQM[7:0]
RAS#
RASB#
CASB#
WEB#
CAS#
WE#
CAS#
WE#
CS2#
S0#, S2#
CS3#
CKEB
S1#, S3#
CKE1
CKE0
SDCLK2
SDCLK3
CK0, CK2
CK1, CK3
Figure 4-4. Memory Array Configuration
www.national.com
104
Revision 3.1
NSC [ National Semiconductor ]
