About GPMC wrapped burst access on AM335x.

RY9983

Hello,

I am interested in GPMC burst access on AM335x.
There are two burst mode.
- Incrementing fixed-length burst
- Wrapped (critical word access first) fixed-length burst

Although I am referenced TRM, I can not imagine about wrapped burst access.
Are there any articles to help?
Or, could you let me know any hints?

Best regards,
RY

over 12 years ago

0 Renjith Thomas over 12 years ago

Guru 31670 points

RY,

Have you tried using DMA? What is the device that is connected to GPMC?

0 RY9983 over 12 years ago in reply to Renjith Thomas

Guru 10570 points

Hello, Thomas.

Thank you for your reply.

Renjith Thomas said:

Have you tried using DMA? What is the device that is connected to GPMC?

Yes, I am using DMA.
So, I can see burst read/write wave on oscilloscope.

I am using AM3359IDK which is no connect on GPMC.

Best regards,
RY

0 Renjith Thomas over 12 years ago in reply to RY9983

Guru 31670 points

RY,

Burst wraparound is enabled through the GPMC_CONFIG1_i[31] WRAPBURST bit and allows a 4-, 8-, or 16-Word16 linear burst access to wrap within its burst-length boundary through GPMC_CONFIG1_i[24-23] ATTACHEDDEVICEPAGELENGTH.

I hope this statement clarifies.

0 RY9983 over 12 years ago in reply to Renjith Thomas

Guru 10570 points

Hello, Thomas.

Thank you for your information of settings of GPMC wrapped burst.
But, I have not understood of operation image of wrapped burst access.
Especially, What is the meaning of description "critical word access first" on TRM?

Best regards,
RY

0 Renjith Thomas over 12 years ago in reply to RY9983

Guru 31670 points

RY,

I'm not 100% sure. But it should be some what like this. Assume that you've only address line A2-A0 connected to a device, the addresses 0x1000-0x1007 will refer to different offsets in the devices. But if I refer to 0x1008, inside the device it will again fall back to offset 0x0. So 0x1000 and 0x1008 is exactly the same for the device and it is different for the host. I think the concept used here will be similar.

I'm not sure about the "critical word" though.

0 RY9983 over 12 years ago in reply to Renjith Thomas

Guru 10570 points

Hello, Renjith.

I am sorry for my late reply.
And, great thanks for your advice.
OK. I understand your explanation.

Thank you again.

Best regards,
RY

0 pathfinder over 12 years ago in reply to RY9983

TI__Genius 12790 points

RY,

Can you provide your GPMC + DMA source code example? Thanks.

0 RY9983 over 12 years ago in reply to pathfinder

Guru 10570 points

Marc-san,

Thank you very much for rechecking my post.
Sorry. Since I am busy now for other work, may I get back to you later?
I appreciate your support.

Best regards, RY

0 Daisuke Maeda over 12 years ago in reply to pathfinder

Guru 20205 points

Hi,

What is the difference between the non-wrapping burst(WRAPBURST bit = 0) and the wrapping burst(WRAPBURST bit = 1)?

Is it only different about the address boundary?

About the non-wrapping address boundary, is it variable?
Is it 2-word boundary at the least?

About the wrapping address boundary, is it fixed?
For example, when the ATTACHEDDEVICEPAGELENGTH field value is 16-word, it is fixed in 16-word.

Best regards,

Daisuke

0 Daisuke Maeda over 12 years ago in reply to Daisuke Maeda

Guru 20205 points

Hi,

I have new question at new post.

http://e2e.ti.com/support/arm/sitara_arm/f/791/t/263909.aspx

Best regards,

Daisuke

0 Mohsen Taheri over 12 years ago in reply to pathfinder

Intellectual 510 points

I need GPMC + DMA source code example, too.

thanks,

Mohsen

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About GPMC wrapped burst access on AM335x.