Re: general questions regarding ARMs

"Michael J. Noone" <nleahcim@xxxxxxxxx> wrote in message
news:1125518864.246836.67700@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Hi - I'm fairly certain I'm going to use an ARM in a project I'm
> working on. I have a good deal of experience with Atmel AVRs, but I
> have never used an ARM before. So I was wondering if you all could
> answer a couple basic questions regarding ARMs:

I've not used Atmel ARM parts but I have used the Phillips ones and the
fundamental principles are the same,. I bought a Keil MBC2100 development
kit which is based around an LPC2129 and has a serial port, CAN controller,
a few LEDs, a pot and a couple of push switches to get you started. It costs
about GBP75 for the board or GBP250 for the board and a JTAG programmer. It
will accept programs via the serial port so you don't have to use JTAG but
if you corrupt it's boot loader then you'll have to get the JTAG probe out.

It ran FreeRTOS quite comfortably and it only took a morning or so using the
FreeRTOS on-line manual to get some tasks up and running. I even managed to
get the serial port to send a few strings.

> 1. programming: My understanding of programming an ARM is that you do
> it with a JTAG cable. I was looking at this one, specifically:
> http://olimex.com/dev/arm-jtag.html as it is fairly inexpensive. Is
> this a good plan? Bad plan? I've also heard of boot-loading. Is this
> possible on Atmel ARMs? if it is, does this only temporarily load code
> into the chip, or permanently load it in the flash?
>
> 2. boot process: when an AVR turns on it begins by executing the first
> line of code in the flash - the reset interrupt. Is this how ARMs work?
> I noticed that the ARMs that I was looking at can only access their
> flash in a single cycle at about half the clock speed - so how would
> executing code work for this? I mean how would it run at double that
> speed if it couldn't access the code? Does all code get loaded into the
> RAM and executed there?
>
> 3. operating systems: in my experience with AVRs I've never had an
> operating system running onboard. Is this what is done on ARMs
> generally? I've noticed that there is ARM Linux - could that run on a
> 55Mhz Atmel ARM based off of a ARM7TDMI with 64KB of memory and 256KB
> of flash? Would this even make sense?
>
> 4. DMA: the chip I'm using boasts about its Peripheral DMA Controller
> (PDC). It says that it greatly reduces the overhead on the processor.
> But reading about it, I am having trouble understanding how DMA differs
> from no DMA.
>
> Sorry for asking so many questions - I'm just very new to the ARM
> world. Thanks!
>
> -Michael J. Noone
>


.

Relevant Pages

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