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Honored Contributor I
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ALTPLL for SDRAM

Hi, 

 

I'm totaly inexperienced with FPGA, Quartus II, SoPC Builder and the whole stuff.  

 

I started with the Altera tutorial Introduction_to_the_Altera_SOPC_Builder and using_the_SDRAM. Helped me to get started but now i have some questions.  

 

First of all, for the system I want to create, i only need NIOS II and SDRAM. I noticed in the SDRAM tutorial that i probably will need a PLL. Now I read some datasheets and dokumentations, also searched in this forum, but didn't found the answer. 

How do I get the right timing for PLL? I found following caldulation: 

 

Max. lag = min(read lag, write lag) 

Max. lead = min(read lead, write lead)  

 

with 

 

Read lag = T[SUB]O[/SUB][SUB]H[/SUB](sdram) - T[SUB]H[/SUB](FPGA)  

Write lag = T[SUB]CLK [/SUB]- T[SUB]CO_MAX[/SUB](FPGA) - T[SUB]ds[/SUB](SDRAM)  

 

Read lead = T[SUB]clk[/SUB] - T[SUB]hz[/SUB](SDRAM) - T[SUB]su[/SUB](FPGA)  

Write lead = T[SUB]co_min[/SUB](FPGA) - T[SUB]dh[/SUB](SDRAM)  

 

Is that right? I found the timing parameters for SDRAM on my board (is42s1632od-7tl) but can't find anything for the FPGA. I'm using DE2-115 Cyclone 4. Please, tell me if I'm on the wrong way, just want to understand this stuff. 

 

PS: sorry for my english
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