LP-AM243: the same Transfer Request Package of UDMA - BCDMA execute for infinite loop

Bolt Hsieh

Prodigy 115 points

Part Number: LP-AM243

Hi expert,

I will use the same TR of BCDMA execute for infinite loop.

And then, I want to skip the time of dequeue & queue again for the same TR.

So, Follow section 11.1.4.16 of the AM243x TRM,

The description of the steps : 1-b & 1-c says the reload function will be enable when the reload-enable sets to 1.

Reload Enable is set to 1 if the Reload Count is non-zero, and Reload Count is described in 11.1.3.2.3 Transfer Request Descriptor.

"Reload Count" = 0x1FF is an infinite loop for repeating TR.

But I cannot match the format of Table11-32 "Transfer Request Packet Descriptor Word0" to Table11-31 "Transfer Request Packet Descriptor Layout".

Hence, I failed to modify App_udmaTrpdInit() to reload the TR again.

So I don't know how to implement the function in my program. Please give me some suggestions or an example for reference.

Best Regards

Bolt

over 2 years ago

0 Frank Livingston over 2 years ago

TI__Mastermind 29408 points

Hi Bolt,

Bolt Hsieh said:
I will use the same TR of BCDMA execute for infinite loop.

And then, I want to skip the time of dequeue & queue again for the same TR.

I believe the example code I shared with you in this thread does exactly what you're describing: https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1196582/lp-am243-how-to-configure-gpio-event-trigger-for-bcdma-operation

Bolt Hsieh said:
Hence, I failed to modify App_udmaTrpdInit() to reload the TR again.

Please see App_udmaTrpdInit() in the example I shared and compare it with the original version of the function in this example: https://software-dl.ti.com/mcu-plus-sdk/esd/AM243X/08_05_00_24/exports/docs/api_guide_am243x/EXAMPLES_DRIVERS_UDMA_MEMCPY_INTERRUPT.html

Bolt Hsieh said:
But I cannot match the format of Table11-32 "Transfer Request Packet Descriptor Word0" to Table11-31 "Transfer Request Packet Descriptor Layout".

It's also difficult for me to understand the TRM. I'm looping in a colleague to help.

It looks like the top portion of Table 11-31 , "Packet Info (16 bytes)" matches up with 32-bit Word0, 1, 2, and 3 described in Table 11-32 - Table 11-35 (4 32-bit words * 4 bytes / word = 16 bytes).

Regards,
Frank

0 Haley Alexander over 2 years ago in reply to Frank Livingston

TI__Intellectual 1475 points

Hi Bolt,

It appears that Frank answered all but the Table-31 vs Table-32 question. For the format question, Word 0 is part of Transfer Request Packet Descriptor Layout, so Frank's assumption of Packet Info is correct. I created this table to better summarize the answer on the Table 11-31 format with relationship to Word 0.

Packet Info – Given via Transfer Request Packet Descriptor Word 0-3 (16 Bytes)

Null (0-102 bytes to bring start of TR request array into natural alignment for memory fetch efficiency)

Array of Transfer Request Records

Array of Transfer Response Records

Thanks,

Haley

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LP-AM243: the same Transfer Request Package of UDMA - BCDMA execute for infinite loop