SDRAM Controller (SDRAMC)
MCF52277 Reference Manual, Rev. 1
19-10
Freescale Semiconductor
19.3.2
SDRAM SDR Connections
shows a block diagram using 32-bit wide SDR SDRAM (such as Micron MT48LC4M32B2)
and flash (such as Spansion AM29LV160D). SDR design requires special timing consideration for the
SD_DQS[3: ] signals. For reads from DDR SDRAMs, the memory drives the DQS pins so that the data
lines and DQS signals have concurrent edges. The SDRAMC is designed to latch data 1/4 clock after the
SD_DQS[3: ] edge. For DDR SDRAM, this ensures that the latch time is in the middle of the data valid
window.
The SDRAMC also uses the SD_DQS[3: ] signals to determine when read data can be latched for SDR
SDRAM; however, SDR memories do not provide DQS outputs. Instead the SDRAMC provides a
SD_SDRDQS output routed back into the controller as SD_DQS[3: ]. The SD_SDRDQS signal should
be routed such that the valid data from the SDRAM reaches the controller at the same time or before the
SD_SDRDQS reaches the SD_DQS[3: ] inputs.
When routing SD_SDRDQS the outbound trace length should be matched to the SD_CLK trace length.
This aligns SD_SDRDQS to the SD_CLK as if the memory had generated the DQS pulse. The inbound
trace should be routed along the data path, which should synchronize the SD_DQS so that the data is
latched in the middle of the data valid window.
2
2
2
2
2
Summary of Contents for MCF52277
Page 22: ...MCF52277 Reference Manual Rev 1 Freescale Semiconductor xxii...
Page 32: ...MCF52277 Reference Manual Rev 0 xxxii Freescale Semiconductor...
Page 60: ...Signal Descriptions MCF52277 Reference Manual Rev 1 2 16 Freescale Semiconductor...
Page 128: ...Static RAM SRAM MCF52277 Reference Manual Rev 1 6 6 Freescale Semiconductor...
Page 140: ...Clock Module MCF52277 Reference Manual Rev 1 7 12 Freescale Semiconductor...
Page 172: ...Chip Configuration Module CCM MCF52277 Reference Manual Rev 1 9 16 Freescale Semiconductor...
Page 180: ...Serial Boot Facility SBF MCF52277 Reference Manual Rev 1 10 8 Freescale Semiconductor...
Page 188: ...Reset Controller Module MCF52277 Reference Manual Rev 1 11 8 Freescale Semiconductor...
Page 210: ...Crossbar Switch XBS MCF52277 Reference Manual Rev 1 13 8 Freescale Semiconductor...
Page 542: ...FlexCAN MCF52277 Reference Manual Rev 1 23 32 Freescale Semiconductor...
Page 724: ...UART Modules MCF52277 Reference Manual Rev 1 30 34 Freescale Semiconductor...
Page 740: ...I2 C Interface MCF52277 Reference Manual Rev 1 31 16 Freescale Semiconductor...
Page 790: ...Debug Module MCF52277 Reference Manual Rev 1 32 50 Freescale Semiconductor...