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Participant hw_42
Participant
895 Views
Registered: ‎12-01-2017

Fine granularity refresh mode with MIG controller

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I checked the PG150, and I have the impression it is not possible to use a mode other than the 1X described in the DRAM datasheet:

Screenshot from 2018-06-07 17-17-46.png

For example, when explaining the refresh command postponing, it uses the maximum number of commands that is possible to postpone in 1X:

 

The DRAM specification allows up to eight refreshes to be postponed, giving you flexibility to schedule refreshes over a 9 × tREFI period
 

Is that really the case with the controller?

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1 Solution

Accepted Solutions
Moderator
Moderator
1,080 Views
Registered: ‎11-28-2016

Re: Fine granularity refresh mode with MIG controller

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Hello @hw_42,

 

The controller is only aware of regular (1x) refresh commands and doesn't have the capability of using the On-the-fly modes because that requires different values to be driven on BG0 when the refresh command is issued. 

 

You can edit the design files and specify a different tREFI and mode register values inside the IP that could possibly get you a Fixed 2x or 4x mode but keep in mind this hasn't been tested by Xilinx so there's no grantee it will work as expected and you must perform your own testing to validate the behavior.  If there are any issues that come up with this when you're on your own to resolve them.

 

Postponing refreshes is a different behavior and you can do that by enabling the User Refresh option when configuring the IP and have a separate piece of logic that tracks the scheduling and insertion of the refresh commands.  PG150 talks about this on page 204 of the latest version:user_refresh.PNG

 

3 Replies
Moderator
Moderator
1,081 Views
Registered: ‎11-28-2016

Re: Fine granularity refresh mode with MIG controller

Jump to solution

Hello @hw_42,

 

The controller is only aware of regular (1x) refresh commands and doesn't have the capability of using the On-the-fly modes because that requires different values to be driven on BG0 when the refresh command is issued. 

 

You can edit the design files and specify a different tREFI and mode register values inside the IP that could possibly get you a Fixed 2x or 4x mode but keep in mind this hasn't been tested by Xilinx so there's no grantee it will work as expected and you must perform your own testing to validate the behavior.  If there are any issues that come up with this when you're on your own to resolve them.

 

Postponing refreshes is a different behavior and you can do that by enabling the User Refresh option when configuring the IP and have a separate piece of logic that tracks the scheduling and insertion of the refresh commands.  PG150 talks about this on page 204 of the latest version:user_refresh.PNG

 

Participant hw_42
Participant
817 Views
Registered: ‎12-01-2017

Re: Fine granularity refresh mode with MIG controller

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@ryanait works. Finally, I modified tRFC only, because my tREFI is already set to zero (user refresh mode).

Mode register was modified as well to select the correct refresh rate.

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Newbie aayush94
Newbie
99 Views
Registered: ‎09-18-2019

Re: Fine granularity refresh mode with MIG controller

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Hi all,

Can the mode register MR3 be changed for fine granularity refresh using tcl?

The answer https://www.xilinx.com/support/answers/71696.html explains how the tRFC, tRFC_dlr and tREFI can be changed through tcl, but I could not find any way of changing the mode register through tcl. Is it possible?

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