Freescale Semiconductor MPC8250, Family Reference Manual

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Memory Controller
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
11-46 Freescale Semiconductor
Figure 11-35. SDRAM Write-after-Write Pipelined, Page Hit
Figure 11-36. SDRAM Read-after-Write Pipelined, Page Hit
11.4.8 SDRAM Read/Write Transactions
The SDRAM interface supports the following read/write transactions:
• Single-beat reads/writes up to double word size
• Bursts of two, three, or four double words
SDRAM devices perform bursts for each transaction, the burst length depends on the port size. For 64-bit
port size, it is a burst of 4. For 32-bit port size, it is a burst of 8. For reads that require less than the full
burst length, extraneous data in the burst is ignored. For writes that require less than the full burst length,
the PowerQUICC II protects non-targeted addresses by driving DQMn high on the irrelevant cycles of the
burst. However, system performance is not compromised since, if a new transaction is pending, the
PowerQUICC II begins executing it immediately, effectively terminating the burst early.
CLK
ALE
CS
SDRAS
SDCAS
MA[0–11]
Column1
WE
DQM
Data
D0 D1
D2
D3 D1 D2 D3 D0
Column2
CLK
ALE
CS
SDRAS
SDCAS
MA[0–11]
Column1
WE
DQM
Data
D0 D1 D2 D3
D1 D2 D3
D0
Column2 Z