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SDRAM Controller (SDRAMC)
Freescale Semiconductor
21-11
21.4.2
SDRAM Control Register (SDCR)
The SDCR (
) controls SDRAMC operating modes, including refresh count and address line
muxing.
Address: 0xFC0B_8004 (SDCR)
Access: User read/write
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R MODE
_EN
CKE
DDR_
MODE
REF_
EN
DDR2_
MODE
0
ADDR_MUX
0
OE_
RULE
REF_CNT
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
MEM_
PS
0
DQS_OE
0
0
0
0
0
0
0
0
0
DPD
W
IREF IPALL
Reset
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 21-5. SDRAM Control Register (SDCR)
Table 21-6. SDCR Field Descriptions
Field
Description
31
MODE_EN
SDRAM mode register programming enable.
0 SDMR locked, cannot be written.
1 SDMR enabled, can be written.
Note:
MODE_EN must be cleared during normal operation,
30
CKE
Clock enable. CKE must be set to perform normal read and write operations. Clear CKE to put the memory in
self-refresh or power-down mode.
0 SD_CKE is negated (low)
1 SD_CKE is asserted (high)
29
DDR_MODE
DDR mode select.
Reserved
1 DDR mode
28
REF_EN
Refresh enable.
0 Automatic refresh disabled
1 Automatic refresh enabled
27
DDR2_MODE
DDR2 mode select.
0 DDR mode
1 DDR2 mode
Note:
If DDR_MODE is cleared, this bit is ignored.
26
Reserved, must be cleared.
25–24
ADDR_MUX
Controls the use of internal address bits A[27:24] as row or column bits on the SD_A bus. See
, and
23
Reserved, must be cleared.
22
OE_RULE
Drive rule selection.
0 Tri-state except to write. SD_D and SD_DQS are only driven when necessary to perform a write command.
1 Drive except to read. SD_D and SD_DQS are only tristated when necessary to perform a read command.
When not being driven for a write cycle, SD_D hold the most recent value and SD_DQS are driven low. This
mode is intended for minimal applications only, to prevent floating signals and allow unterminated board
traces. However, terminated wiring is always recommended over unterminated.
Содержание MCF54455
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