🚀 go-pugleaf

On Fri, 30 Oct 2009 15:43:58 +0000, Raveninghorde
<raveninghorde@invalid> wrote:

>On Fri, 30 Oct 2009 06:52:49 -0700 (PDT), MooseFET
><kensmith@rahul.net> wrote:
>
>>On Oct 30, 4:57�am, Al Borowski <al.borow...@gmail.com> wrote:
>>> > Briefly, the Modified-Harvard architecture used in the PIC devices
>>> > separates the program memory from the data memory, in other words
>>> > separates the ROM/FLASH program memory from the RAM.
>>>
>>> [...]
>>>
>>> Yes, but there's more to to a uC core then choosing between Harvard or
>>> Von Neumann. I think most of the PICs quirks come from the other
>>> decisions made.
>>>
>>> The PIC (up to 16 bit cores anyway) is an accumulator architecture -
>>> you have to funnel everything through the W register.
>>
>>Going with accumulator model allowed Microchip to make the processor
>>with fewer transistors. It is a trade off that can break either way.
>>If you have a limit on the chip size you can make a higher performance
>>processor that is harder to program.
>>
>>
>>[....]
>>> in the 16 bit core thankfully). Personally, I think the most annoying
>>> thing about programming PICs in assembly are the btfsc (test a bit in
>>> 'file', skip the next instruction if it's clear) and btfss (same thing
>>> but skip if set) instructions. Why they couldn't just call these ifbit
>>> and ifnbit, I don't know :-)
>>
>>Does ifbit mean skip if the bit is set or do the instruction if the
>>bit is set?
>>
>>>
>>> Back to the OP, great job Microchip on the video. It's a nice contrast
>>> to TI, who recently sent misleading DMCA notices to people who tried
>>> installing after-market OSs on their graphics calculators (http://news.cnet.com/8301-30685_3-10374284-264.html)
>>>
>>> Cheers,
>>>
>>> A;
>>
>>I still prefer the 8051.  It is way better.
>>[ducks]
>
>So do I. The 8051 family was/is great.

I'm using one from SiLabs, right now.  Last 8051 project I did was
back in the early 1980's.  (Still have a box of about 100 80C32 chips
in perfect shape.)  For this app, I needed a much faster floating
point ln(x) function (achieved under 18 microseconds) and found myself
spending some time coding assembly on it.  No question in my mind that
this processor was designed with hand-coded assembly in mind, though.
Very easy to use efficiently for a human coder, though I do have to
check the book often to see if a particular instruction supports a
particular mode of access, yet just the kind of thing to seriously
complicate a compiler's life.

>But I found the varients of 8051 I used were obsolete on more than one
>occassion causing problems. I'm still sourcing SAB80C517 at silly
>prices for example.

I gather that Atmel has an AT89 line that includes an external bus and
so does SiLabs.  Not sure how either of these would score on not
obsoleting designs, though.

>I first used the PIC for very low cost apps around 1990 and found that
>there was always an upgrade path which didn't obsolete my designs.

Yes.  I've been using PICs since the late 1980's.. just around the
very month that Parallax entered the public fray.  Nobody likes the
bare-bones ALU design for the smaller-width instruction families --
it's design guts lay out on the floor, plain to see.  But Microchip
has maintained a very serious commitment to upgrade pathways over the
entire time I've been involved (just after they decided to move beyond
the "million unit rice cooker customer" days and place them into a
broader marketplace.  I couldn't have guessed then how strong that
commitment would be.  But they seem to well know what is important and
they have clearly (to me) worked very hard to _earn_ the respect they
have gained.  And it's been so on almost every good business front.

One begins to realize after experiencing such a company's commitment
to their customers, if that realization isn't already at hand, just
how relatively unimportant an instruction set is to all these other
business factors.

>Secondly Microchip always have product available.  I recall one rep
>trying to convert me to the ST6. Then he said ST are behind on
>production and delivery was 4-6 months.

Well, Microchip has had their days with delays (the wait for the
18F252 from using the 18C252 comes to mind) but they have tended to be
shorter than longer delays.

>There are better micros than the PIC from an engineering perspective
>but they are hard to beat from a production view point.

In all the time I've used them, they have consistently maintained a
solid professional use pathway that simply doesn't break.  I have old
tools that they no longer make (ProMate II) and yet they still support
it without question or quibble.  If I have so much as a flaky power
switch they want me to send it in and fire off a replacement with
shipping included for the "bad" one, so that I don't even miss a
single second of use.  Same for the modules that plug into it.  Their
tools are supported, decades it seems after they don't sell them
anymore.  That takes commitment on their part.

I find wringing of hands over the instruction set to be relatively
badly placed.  There are a lot more important things to focus on and
on those areas Microchip has done a yeoman's service across the board.

Obviously, I use other manufacturers too.  It's _very_ hard to find a
1MHz 16-bit SAR ADC anywhere in Microchip's monolithic cpu fold, for
example.  But none of have compared quite as well on the business
issues over the years.

Jon