ColdFire/68K Microcontrollers and ProcessorsのトピックRe: MCF5485 DMA DRD and LCD Documentation

MCF5485 DMA DRD and LCD Documentation

mthrock1 — Thu, 22 Mar 2007 00:55:22 GMT

The MCF548x Reference Manual mentions the data structures used in the Multi-channel DMA task descriptor table, namely "Data Routing Descriptors" and "Loop Control Descriptors" (section 24.3.1.2). It also mentions the Function Descriptor Table (section 24.3.1.4). Does anyone know where I can find complete documentation of these descriptors? The Freescale provided DMA API contains several tasks (and an easy way to use them), but I have some special processing needs that I suspect the DMA engine could provide if I knew how to write my own descriptors.

Thanks,
Mike

Re: MCF5485 DMA DRD and LCD Documentation

JWW — Thu, 29 Mar 2007 12:33:33 GMT

Mike,

I can't quite tell from your message if you've inherited some code in a BSP or example code from somewhere and are missing the docs, or if you already have the docs.

So I apologize if you have already found this file.

Follow this link to download the DMA's API and docs.

http://www.freescale.com/webapp/sps/download/license.jsp?colCode=MCDAPI&prodCode=MCF5485&nodeId=0162468rH3YTLC00M93426&location=psp

OR

Go to the 5485's product page.
And do a "control-F" or "find" for "MCDAPI"

Now.. if I assume you already have this... And you need some special functions that manipulate the DRDs or LCDs in a different manner, then I'm not sure I can help you. If you enter a service request, maybe we can find a way to solve your problem with the current API in a way that may not be obvious.

Hope this helps.

-JWW

Re: MCF5485 DMA DRD and LCD Documentation

mthrock1 — Thu, 29 Mar 2007 21:46:05 GMT

Sorry I wasn't clear. I have all the MCD API docs and the associated code. I want to do some things that aren't possible in the context of the Freescale provided API, so I was hoping to write my own DMA tasks, or possibly modify the API tasks. It's the DRD and LCD elements of those tasks (and the function descriptors, too) that are undocumented. I was told that there was no documentation published because (if I may paraphrase), it's too complicated for us ordinary user types.

Thanks,
Mike

Re: MCF5485 DMA DRD and LCD Documentation

JWW — Fri, 30 Mar 2007 12:34:53 GMT

Mike,

Don't take it the wrong way.. It's too complicated even for those of us that are suppose to understand it. The reason we released the API, was to minimize the chance of customers having implementation problems. The DMA engine is very powerful, but it is effectively a micro-coded state machine and its programming model is less than ideal... We have to do a lot of testing before releasing an API..The API as it stands today is quite stable.

One of the drawbacks to micro-coded state machines or VLIW architectures is typically the programming model. They can do really neat things in a typically faster manner than a traditional programmable machine, but can be quite complicated to program.

May I ask for more details of your original request? I can't promise anything, but sometimes we've found alternative ways to solve the problem without actually changing the code. Or maybe somebody in the community has tried to solve the same problem and has found a way around it.

Thanks

-JWW