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SDRAM Controller (SDRAMC)
Freescale Semiconductor
21-23
21.5.1.6.5
DDR2 Extended Mode Register Set (1)
shows the extended mode register used by DDR2 SDRAMs. This is the SDRAM’s extended
mode register, and not the SDRAMC’s mode/extended mode register (SDMR) described in
“SDRAM Mode/Extended Mode Register (SDMR)
A8
DLL
DLL mode
0 Normal
1 Reset DLL
A7
TM
Test mode
0 Normal
1 Test Mode
A6–A4
CL
CAS latency. Delay in clocks from issuing a
READ
to valid data. Check the SDRAM manufacturer’s spec
as the CL settings supported can vary from memory to memory.
A3
BT
Burst type
0 Sequential
1 Interleaved. This setting should not be used because the SDRAMC does not support interleaved
bursts.
A2–A0
BL
Burst length
010 4
011 8
BA1
BA0
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Field
0
1
Q
off
RDQS DQS
OCD program
R
tt
Additive Latency
R
tt
D.I.C.
DLL
Figure 21-13. DDR2 Extended Mode Register (1)
Table 21-15. DDR2 Extended Mode Register (1) Field Descriptions
Field
Description
BA1–BA0
Bank address. Must be set to 01 to select the DDR2 Extended Mode Register (1).
A12
Q
off
Output buffer disabled. Disables DQs, DQSs, DQSs, RDQS, RDQS. This feature is used with dimm IDD
measurements when IDDQ is not desired to be included.
0 Output buffer enabled
1 Output buffer disabled
A11
RDQS
RDQS enable. If RDQS is enabled, DM function is disabled. RDQS is active for reads and don’t care for
writes. Used in conjunction with DQS to produce the strobe function matrix in
0 Disable
1 Enable.
A10
DQS
DQS enable. Enables the DQS signals to be used for data strobes.
0 Enable
1 Disable
Table 21-14. DDR2 Mode Register Field Descriptions (continued)
Field
Description
Содержание MCF54455
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