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DDR2, confused about the write data pattern

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hastidot

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Hi all

I'm using MIG 3.4 for DDR2 controlling on virtex5.

I'm trying to write my own codes to write and read from memory.



As I am new to MIG ( and working with DDR2), I tried to follow the patter which is used as the MIG's synthesizable testbench uses. I read the UG086 many many times but i'm still confused about the data pattern ( and subsequently the address generation pattern).

As it is indicated in UG086:

The MIG test bench performs eight write commands and
eight read commands in an alternating fashion. The number of words in a write command
depends on the burst length. For a burst length of 4, the test bench writes a total of 32 data
words for all eight write commands (16 rise data words and 16 fall data words).





While generating my design, I chose the data width as 8, my DQ-width parameter is equal to 64 ( I'm confused about the relationship of these two parameters. which shows my design data width?), and the busrtlength=4.



First question:

I don't understand what is that: 8 consecutive read and write commands. As I can see in simulation results, the app_af_cmd is 0,1 periodically. What does it mean with 8?



Second:

I'm totally confused about the data patter. 32 data words (16fall and 16 rise) is interpreted as : FFFFFFFFFFFFFFFF0000000000000000

But what I see in siumlation is repetition of 16 data words like this in a write or read command. (means 16*128 bits of data in app_wdf_data !!!!!!!!!!!!!!!!!!!!!!!! )



Question 3:



As the BL=4, The address should be changed 4 times in a single write or read command. But it is changed 8 times in the simulation results.





Following is my simulation result (the ddr2_tb_top simulation result)

Please help me understand the manner:



The small rectangular in app_wdf_data are all 128 bits (I wanted to show you the number of data in each command so I had to zoom out the result)



it is something different from what is mentioned in the document.
 

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