Interfacing OMAP-L138 with SDRAM

Please see the appendix A (pg 74) of the TMS320C674x/OMAP-L1x Processor External Memory Interface A (EMIFA) User's Guide for example configurations to existing memories (Samsung K4S641632H-TC(L)70 64Mb and SHARP LH28F800BJE-PTTL90 8Mb)

Mariana,

Thank you for your fast replay.

However OMAP-L138 document http://www.ti.com/lit/gpn/omap-l138 SPRS586–JUNE 2009 (Table 6-18, page 95) claims that OMAP-138L supports SDRAM size starting from 256Mb while appendix A (pg 74) of the TMS320C674x/OMAP-L1x Processor External Memory Interface A (EMIFA) User's Guide describes Samsung SDRAM K4S641632H-TC(L)70, which size is 64Mb only. I suspect that 64Mb SDRAM will not work with OMAP-L138 since its size is lower than minimal SDRAM size, supported by OMAP-L138.

Igor S. said:

I suspect that 64Mb SDRAM will not work with OMAP-L138 since its size is lower than minimal SDRAM size, supported by OMAP-L138.

It seems you may be right, in particular we specify support only for SDRAM devices that have 13 row address bits however the K4S641632H appears to have only 12 row address bits which could lead to addressing problems, I have never tried using a smaller SDRAM than was supported before so I am not sure exactly what will happen though. We will be checking internally to see if we can get this clarified and the documentation updated.

I think the table in the data sheet has been misinterpreted.  The table does give the configurations supported by the EMIF, and the maximum amount of memory supported under each configuration.  However, there is some flexibility in that you don't need to use all the row bits.  Column & bank bits are required though.  The reason for this is that the highest row bit used depends on the amount of memory you have on the board.  You can kind of see this from Table 13 in SPRUFL6.  In this case, you should leave unused EMIF address pins unconnected.