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Honored Contributor I

Regarding SD RAM controller IN DE2

I need information about how to use SD RAM controller since I need to implement in my project. I need to understand the signal flow from Controller to SDRAM. So i need some content or links to help myself clearly understand the controller signals. Thanks in advance!!

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Honored Contributor I

If you want the university program signals I can't help as I never got it to work, however, SRAM signals are pretty easy to understand, check the data sheet that same with the board and you can either control it with PIO signals if you're using Nios. Understanding the signals also lets you control flow in hardware if needed. 


From my understanding (as it is probably not yet complete) control goes as follows: 


There are control signals, all active low 

ce_n : Chip Enable 

we_n : Write Enable 

oe_n : Read Enable 

ub_n: Upper Byte Enable 

lb_n : Lower Byte Enable 


As well as data lines: 

dq : Data Line(s) 

addr: Address Line(s) 



There are three main states I use: 



Control Lines high (ce_n, we_n, oe_n, ub_n, lb_n


writing to sram 

1. Put desired Address on addr lines 

2. Put desired data on dq lines 

3. Drop desired bytes (ub_n, lb_n) followed by chip enable and write enable (ce_n, we_n

4. Wait for data to latch (check data sheet for timing, my clock rate is slower than the latch time so I skip this step) 

5. Raise control signals 


reading is similar 

1. Put Address on addr lines 

2. Drop desired bytes (ub_n, lb_n) followed by chip enable and read enable (ce_n, oe_n

3. Wait for data to be available on dq lines (see step 4 above) 

4. Obtain the data (data = dq

5. Raise control signals 


With the waveforms in the datasheet you should be able to determine which signals to use for which control on the SRAM, or write your own library, maybe even get the UP core working if that's you goal.You're also responsible for controlling data to and from the DQ line as it's bidirectional. This was a source of confusion at first for me. Hope this helps!
Honored Contributor I

Wow! Thanks a lot for a very nice reply... Thats what i was looking for! :D