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662 Views
Registered: ‎05-07-2018

DDR4 SDRAM 2.2 - multiple values of CAS write latency

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Hello,

I'm trying to add custom Hynix part definition for DDR4 MIG IP core using custom .csv file using Vivado 2017.4. For now I have downloaded example file custom_parts_ddr4_2016_4.csv from Xilinx resources and after playing with it, I appended my custom part, for which I would like to define all CAS latency and CAS write latency values handled by part (9-20 CAS latency and 9-18 CAS write latency).

For now my line yields:

Components,DDR4_HYNIX,1,1,0,1,17,16,10,2,1,1,1,1,1,UH,2GB,16Gb,16,16,8,1.2V,"8,16,24,32,40,48,56,64,72,80",833,1600,5000 ps,30000 ps,0,8 tck,34000 ps,13920 ps,7800000 ps,260000 ps,0,13920 ps,5300 ps,6400 ps,0,7500 ps,15000 ps,2500 ps,7500 ps,270 ns,128 tck,1024 tck,0,"9,10,11,12,13,14,15,16,17,18,19,20",9,8

For now CAS latency drop-down list works fine, but if I try to create list for CAS write latency, like:

Components,DDR4_HYNIX,1,1,0,1,17,16,10,2,1,1,1,1,1,UH,2GB,16Gb,16,16,8,1.2V,"8,16,24,32,40,48,56,64,72,80",833,1600,5000 ps,30000 ps,0,8 tck,34000 ps,13920 ps,7800000 ps,260000 ps,0,13920 ps,5300 ps,6400 ps,0,7500 ps,15000 ps,2500 ps,7500 ps,270 ns,128 tck,1024 tck,0,"9,10,11,12,13,14,15,16,17,18,19,20","9,10",8

importing .csv file gives me warning:

[Mig 66-120] Custom Part (DDR4_CUSTOM) with parameter: cas write latency having value: 12,13 is invalid. The valid values for cas write latency are 9, 10, 11, 12, 14, 16, 18 and 20. cas write latency value must be less than or equal to cas latency value.

I can workaround this issue by declaring final values in .csv, but what is the use for drop-downs in DDR4 IP then...

 

Best regards

MKu

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824 Views
Registered: ‎02-11-2014

Re: DDR4 SDRAM 2.2 - multiple values of CAS write latency

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Hello@mkurczalskifpi,

 

The custom CSV flow is meant to be a point solution. It does not take into account the operating frequency, so whenever you change the operating frequency you need to manually update your CWL/CL in your custom CSV. The CWL/CL field is only designed to take in a single value and not a string of values. The only filed in the custom CSV that can take multiple values is Data Width.

 

CWL and CL is VERY dependent on operating frequency, so please be careful when using a custom CSV.

 

Thanks,

Cory

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3 Replies
Moderator
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825 Views
Registered: ‎02-11-2014

Re: DDR4 SDRAM 2.2 - multiple values of CAS write latency

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Hello@mkurczalskifpi,

 

The custom CSV flow is meant to be a point solution. It does not take into account the operating frequency, so whenever you change the operating frequency you need to manually update your CWL/CL in your custom CSV. The CWL/CL field is only designed to take in a single value and not a string of values. The only filed in the custom CSV that can take multiple values is Data Width.

 

CWL and CL is VERY dependent on operating frequency, so please be careful when using a custom CSV.

 

Thanks,

Cory

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610 Views
Registered: ‎05-07-2018

Re: DDR4 SDRAM 2.2 - multiple values of CAS write latency

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Hello @coryb,

 

Thank you for your response. I am going to use CSV as point solution, however I am not entirely sure why workflow with custom CSV is designed this way. The fact that CWL/CL are operating frequency related, which is a range from <1/max period> to <1/min period>, was the reason why our team wanted to have all possible values for this parameters in part description, so that we would not have to check it within datasheet. On top of that, parts for which description is provided by default do have multiple values on respective combo boxes. Moreover, although you mentioned Data Width as only field which accepts multiple values, this strategy works perfectly for CL field as well.

So personally I feel like it is a missing feature or a bug, certainly an area to tweak, but for the time being I am going to specify single CL/CWL values.

 

Best regards

MKu

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Registered: ‎02-11-2014

Re: DDR4 SDRAM 2.2 - multiple values of CAS write latency

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Hello @mkurczalskifpi,

 

I was receiving warnings in the Messages Tab for when CL and/or CWL had more than one value and the custom CSV area of the DDR4 IP was "red" with a note to look at the Messages Tab for issues. We can only adjust CL/CWL based on frequency with native devices. That has always been a limitation with the custom CSV flow.

 

Thanks,

Cory

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