MCU Selection - S12 S12-XGATE

[EmbeddedCoder]

Hi all,

I am at present doing some forward thinking for a next generation of products.

Previously I have used HCS12 and HCS08 devices, and have code that is tested and ready for use in future products.

What I want to know is - which MCU family gives the best value / performance for money?

I am thinking the logical step is going to some of the XGATE devices - but how much faster are these than the "standard" HCS12 devices (specifically in terms of number crunching algorithms) and what is the sort of cost differential I can expect (i.e. not much / considerable)?

Are there any other gotchas I should be aware of (i.e. are XGATE devices better than HCS12 in every way, or has there been some compromise)?

Also, what is the compatibility of peripherals between HCS12 and XGATE (I'm thinking very good)?

Or would I get more value for money going to the cheaper end of the Coldfire architecture instead (it certainly seems that you get a lot of performance, to the point of having MAC and possibly even FPU at the upper cheap end) - and if so, how compatible are the HCS12 peripheral drivers I have already have in my toolbox of useful to Coldfire?

Or is there another alternative I've not considered?

Thanks for your help,

Mike

[Lundin]

Freescale and every other silicon manufacturer generally keep the lowest prices on new products, because they want to produce the new good pieces and not the old crappy ones.

S12X is therefore currently cheaper than an old S12 with the same memory size. For how long that will last, we can only guess.

I don't know how many "MIPS" and other such fuzzy saleterms you can get out of an S12X, but judging from the oscillator frequency, it will roughly be at least 4 times faster, and then some further efficiency because of the xgate.

S12X is better in every way, unless you pick the part directly after release, because then you'll have to sort out the mandatory silicon bugs. But since 12X has been out for some years, those should however have been taken care of by now.

S12X is pin-compatible with S12. I have yet to see two MCU derivates that are code compatible with each other. There is always some memory mapping or peripheral hardware working differently. But they are compatible on core level, and porting will come with minimal pain as most peripherals are roughly the same. Porting to some completely different architechture like Coldfire or non-Freescale sounds a lot more painful. And of course, if you have written the code in assembler you don't even have that option.

Main disadvantage so far has been that if you are using CW, you have to pay a fortune for a new compiler when moving to S12X, in case you are using an older CW version. Ie, pay again for the compiler you have already payed for, while the other MCU manufacturers give away compilers for free.

But I don't think you have to do that no longer, since Freescale did a license makeover earlier this autumn. I -think- you should be able to download a license and the latest CW for free if you have already payed for CW in the past.

Message Edited by Lundin on 2008-11-06 11:42 AM

[EmbeddedCoder]

Hi Lundin,

Thanks for your information - this is just the sort of level of info I was looking for.

I've just been hunting around and you are right - the new Metrowerks licensing scheme means you can get the IDE you need for free (based on the previous costly license you already own of course!)

My only concern was the lifetime of the S12 / S12X families in general - our products will have a planned lifetime of around 10 years...

Added to that, what is the likelihood of significant silicon development continuing on the S12 / S12X families - are future Freescale priorities the 8 / 32 bit families that make up the controller continuum?

Perhaps there is a Freescaler that could comment on this?

[Lundin]

If you are only concerned about whether the micro will be available or not, you don't need to worry. Look at the HC11 which has been around for almost 20 years now and is still sold. And when they finally close the line, they will sell it to Rochester Electronics or a similar company, which will continue to maintain the part.

The question is rather how much you are prepared to pay for it 10 years from now. Freescale won't stop selling HC12(X) 10 years from now, but they will most likely raise and raise the price on them.

[EmbeddedCoder]

Plus, reading the post at the top of this forum - "Controller Continuum" - it seems doubtful that the technology of 16 Bit Freescale devices will continue to be developed in any meaningful way. Is it better to take the plunge and consider Coldfire.

From what I read on FSL datasheets (contrary to some posts on the forum) Coldfire does support BDM - am I wrong, or do some Coldfire devices support BDM, others JTAG etc?

Also, I'm thinking that IDE support will not as painful or expensive now that I have a copy of Metrowerks for HC12 and am used to its idiosyncraties - from what I understand, Metrowerks licensing now means that if you have a copy for one processor family you are automatically entitled to a copy for the other processor families - i.e. you buy a suite of products, not just the one you need here and now!?

[Lundin]

Regarding the future of the 16-bits, I don't think the development will stop any time soon. The automotive industry wants them, and Freescale is the leading 16-bit manufacturer in the world.

Though of course 16-bit data bus combined with the painful 24-bit addressing (paging) is one major flaw, that will ultimately be the doom of the 16-bits. I don't think we will see that happen in the next 10-20 years however.

Message Edited by Lundin on 2008-11-06 11:50 AM