DMA to/from eLB Devices (UPM Mode) stucks

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DMA to/from eLB Devices (UPM Mode) stucks

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Tilman
Contributor I

Hi,

we are running a Hardware which is similar to the P1020RDB-PD and would like to transfer data from an external SRam Device to/from the CPU SDRam Memory.

If I setup a DMA with length of 16Bytes or less, anything works fine. If I use more then 16 Bytes, the DMA Controller states an Error (bit TE of DMA_SRn Register set).

The external Device is attached to the eLB configured in UPM Mode.

Thks for your time.

Tilman

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LPP
NXP Employee
NXP Employee

In your case, DMA with length of 16 bytes is performed as single-beat teansaction. If you configure more than 32 bytes then burst transactions can be issued.

You can verify this supposition by disabling burst transfers by setting ORn[BI].

Please, refer to P1020RM 12.4.4.1.1 "Memory access requests"

UPM executes single-beat or burst patterns (when BI=0) based on the attributes of original CSB transaction. If BI=1 then burst patterns are never used.

DMA automatically switches between single-beat and burst modes depending on the address alignment and DMA size.

The algorithm is shown in RM Figure 13-95. DMA initiates burst if the address is 32B aligned and block size is >=32. Otherwise, single beat transactions are issued.

My opinion is that you use wrong UPM RAM pattern for burst transactions (offset RBS,WBS). Please check that it provides correct number of UTA bits, so that, total size is 32 bytes: 8 bit device should use patterns with 32 entries UTA=1, 16 bit devices should use patterns with 16 entries UTA=1.

"The user must ensure that patterns for single-beat transfers contain one, and only one,

transfer acknowledge (UTA bit in RAM word set high) and for a burst transfer, contain

the exact number of transfer acknowledges required."


Have a great day,
Pavel

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Tilman
Contributor I

Hi Pavel,

in the meantime, I did some investigation by myself and found out that indeed the BI bit seems to do the trick.

Thanks again for all your time.

BR

Tilman

Mit freundlichen Grüßen / With kind Regards

Tilman Jurk

Tel. +49 (0)7251-75 5406

Von: LPP

Gesendet: Dienstag, 25. November 2014 10:26

An: Jurk, Tilman (EET-IC)

Betreff: Re: - DMA to/from eLB Devices (UPM Mode) stucks

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DMA to/from eLB Devices (UPM Mode) stucks

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