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Forum: FPGA, VHDL & Verilog SDRAM read problem


SDRAM read problem
von 94onur94 (Guest)

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Hello guys, I'm working with the IS42S16400 model 64-Mbit SDRAM that I 
have. I write 16-bit data to random addresses and read. It's okay to 
write, but I'm having trouble on the reading side. I used the SDRAM 
controller model in the link. The friend who designed it used 
IS42S16160G. I changed the timing and address sizes according to my own 
integration.

constant CL : integer := 2;
constant tRCD : integer := 2;
constant tRP : integer := 2;
constant tRAS : integer := 4;
constant tRC : integer := 7;
constant tREF : integer := 64;

In the test program I designed, I printed the values ​​I specified in 
the addresses below and then had them read.

Address -> Value

1024    -> 3000 + state

2097152 -> 16000 + state

2048    -> 12000 + state

8192    -> 6800 + state

16384   -> 1800 + state

32768   -> 5862 + state

As seen in the picture true_read.PNG, the data I wrote was read 
correctly.

However, if I change any address or address content and read, the 
address content is read incorrectly.
I changed the address content of 2097152 to 19000. He read this address 
correctly, but read 1024 as 1814. false_read.PNG

Sometimes it reads incorrectly on the first load. Why is it reading 
incorrectly this way?

SDRAM: https://bertantaskin.com/fpga-ile-sdr-sdram-kontrolu/

SDRAM Test: 
https://github.com/onur94/FPGA/blob/master/SDRAM_Controller_Fifo.vhd

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Re: SDRAM read problem
von Duke Scarring (Guest)

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If I understand you correctly you have a problem with your simulation, 
right?
With the simulator you can usually check the content of your RAM to see 
if the problem on read or on write.

Duke

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