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ADSP-21489 SDRAM connection

Question asked by Laskov_C on Dec 2, 2016
Latest reply on Dec 23, 2016 by Jithul_Janardhanan

Hi, dear AD team.




In present moment I'm working with your DSP solution - ADSP-21489.


And I have some questions about connection of SDRAM to this chip.


As we can find from its datasheet:



This chip has only one data masking output  signal - pin 1 in LQFP176

packaged device.


As we all learned in high schools, data masking is used in SDRAM for masking

one separate byte in whole data word.


This gives the possibility to shorten correction operations.


Except reading word from RAM, changing it and it writing back you can just

change one byte in this word.


In case of ADSP-21489 we have only one masking pin, except two as usually.

But data bus has 16 bits width (data word length as I can understand will be

the same).


So I can't understand how this signal is working.


On your evaluation board it is connected in next manner:




So, for me this mean that this three zero resistors can be soldered for next



R510 + R511 + R509 - short (funny result)


R510 - all data are always masked (useless one)


R511+R509 - all data are always unmasked (possible in case ADSP not performs

correction operations)


R509 only - unexplainable result




And if we look in Micron's memory chip (MT48LC16M16A2) datasheet we will

find next diagram:






So, I can't understand how this solution is working.


For me this is only one possible explanation - this DSP doesn't support

correction operations and this pin is useless.


But, I think this is wrong.




When I was speaking with Russian support team, I was asked to represent

myself in this letter.


So, this is it:


About me -  I'm free researcher from Russia working for myself for food (as

most engineers in Russia)).


In present moment I'm with my friend developing some DJ's equipment.


My site:






Laskov C.