SDRAM Controller (SDRAMC)
21-12
Freescale Semiconductor
21.4.3
SDRAM Configuration Register 1 (SDCFG1)
The 32-bit read/write SDRAM configuration register 1 (SDCFG1) stores necessary delay values between
specific SDRAM commands. During initialization, software loads values to the register according to the
selected SD_CLK frequency and SDRAM information obtained from the data sheet. This register resets
only by a power-up reset signal.
21–16
REF_CNT
The average periodic interval at which the controller generates refresh commands to memory; measured in
increments of 64
SD_CLK period.
REF_CNT = (t
REFI
/ (t
CK
64)) - 1, rounded down to the next integer value.
If the SDRAM data sheet does not define t
REFI
, it can be calculated by t
REFI
= t
REF
/ #rows.
15–14
Reserved, must be cleared.
13
MEM_PS
Memory data port size.
0 Reserved
1 16-bit data bus
12
Reserved, must be cleared.
11–10
DQS_OE
DQS output enable. Each bit of the DQS_OE field is a master enable for the corresponding SD_DQS
n
signal.
DQS_OE[1] (SDCR[11]) enables SD_DQS3 and DQS_OE[0] (SDCR[10]) enables SD_DQS2.
0 SD_DQS
n
can never drive. Use this value in DDR mode with a single DQS memory. Some 32-bit DDR
devices have only a single DQS pin. Enable one of the SD_DQS
n
signals and disable the other. Then, short
both pins external to the device.
1 SD_DQS
n
can drive as necessary, depending on commands and SDCR[OE_RULE] setting. DDR only.
9–3
Reserved, must be cleared.
2
IREF
Initiate refresh command. Used to force a software-initiated refresh command. This bit is write-only, reads return
zero.
0 Do not generate a refresh command.
1 Generate a refresh command. All SD_CS
n
signals are asserted simultaneously. SDCR[CKE] must be set
before attempting to generate a software refresh command.
Note:
A software requested refresh is completely independent of the periodic refresh interval counter. Software
refresh is only possible when MODE_EN is set.
1
IPALL
Initiate precharge all command. Used to force a software-initiated precharge all command. This bit is write-only,
reads return zero.
0 Do not generate a precharge command.
1 Generate a precharge all command. All SD_CS
n
signals are asserted simultaneously. SDCR[CKE] must be
set before generating a software precharge command.
Note:
Software precharge is only possible when MODE_EN is set.
Note:
Do not set IREF and IPALL at the same time.
0
DPD
Deep power-down mode. This bit is only applicable for mobile-DDR (LPDDR) devices.
0 No effect or exit from deep power down-mode
1 Generate a deep power-down mode command. All SD_CS
n
signals are asserted simultaneously
Table 21-6. SDCR Field Descriptions (continued)
Field
Description
Summary of Contents for MCF54455
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Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
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Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
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