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Signal Descriptions
2-12
Freescale Semiconductor
2.3.5
SDRAM Controller Signals
describes signals used for SDRAM accesses.
Table 2-7. SDRAM Controller Signals
Signal Name
Abbreviation
Function
I/O
SDRAM Address Bus
SD_A[13:0]
Address bus used for multiplexed row and column addresses during
SDRAM bus cycles.
O
SDRAM Data Bus
SD_D[31:16]
Bidirectional, non-multiplexed data bus for SDRAM accesses.
I/O
SDRAM Bank Address
SD_BA[1:0]
Selects one of the four SDRAM row banks.
O
SDRAM Clock Enable
SD_CKE
SDRAM clock enable.
O
DDR SDRAM Clock
SD_CLK
Output clock for DDR SDRAM.
O
DDR SDRAM Clock
SD_CLK
Inverted output clock for DDR SDRAM.
O
SDRAM Chip Selects
SD_CS[1:0]
SDRAM chip select signals.
O
DDR SDRAM Data Strobes SD_DQS[3:2]
Indicates when valid data is on data bus.
I/O
SDRAM Write Data Byte
Mask
SD_DQM[3:2]
Used to determine which byte lanes of data bus should be latched
during a write cycle.
The SD_DQM
n
should be connected to individual SDRAM DQM
signals. Most SDRAMs associate DQM3 with the MSB, in which case
SD_DQM3 should be connected to the SDRAM's DQM3 input.
O
SDRAM Column Address
Strobe
SD_CAS
SDRAM column address strobe.
O
SDRAM Row Address
Strobe
SD_RAS
SDRAM row address strobe.
O
SDRAM Write Enable
SD_WE
Indicates direction of data transfer on bus for SDRAM accesses. A
logic 1 indicates a read from a slave device and a logic 0 indicates a
write to a slave device.
O
SDRAM Voltage Reference SD_VREF
Reference voltage for differential I/O pad cells. Should be half the
voltage of the memory used in the system. For example, 2.5 V DDR
results in an SD_VREF of 1.25 V. See the device’s datasheet for the
voltages and tolerances for the various memory modes.
I
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
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 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...