Re: Wich 16-bit MCU?

Robert Latest wrote:
Hello,

I'm now at the point where I'll have to dive into building an embedded
data acquisition system. Last time I did that was about 15 years ago --
burn-and-crash with an 68008 and an EPROM, much along the lines of
Chapter 11 in AoE (just to illustrate the point at which my uC knowledge
froze over).

What I need to do, in real-time, is this -- just to estimate the workload the CPU has to cope with:

1. Read out one 16-bit ADC at 60 kHz rate, do a bit with the numbers and write back out to an ADC at the same rate. This is a PI servo loop that also could be done in analog hardware if the CPU isn't up to it.

2. Read out three 16-bit ADCs at 20kHz rate and store results in RAM
3. Update two 16-bit DACs at 20kHz (numbers come from a couple of Bresenham's algorithms).

4. simple link to host Computer, 800kB/sec (SCSI?)

Task 1. must run continuously. Tasks 2 and 3 run simultaneously but alternatingly with 4.

Based on what I've done I'm partial towards the 68k assembler, so I looked at Freescale's website and found the aged, but pretty attractive MC68332 MCU. Then there's their Coldfire product line which seems to be a bunch of faster/cheaper variants of the same theme.

My problem is getting started with all this. I don't want to drag the old EPROM burner out of the basement; I think the latest fad (late as of probably 15 years ago) is in-circuit programmability and -debugging.

I'm just wondering into which architecture should I invest time and
money in terms of a development system, and how much. Unfortunately the
app notes I found on many MCU vendors mainly cover embedded networking
applications and not the more down-to-earth stuff I'm interested in. Like I said, I like m68k assembler but I've heard good things about ARM, too.

Thanks,
robert

With modern devices you would not normally be working in assembler (unless you are using a very small device). However, if you like assembler (either for programming, or just to view the generate assembly), then few ISAs are nicer than the m68k. It's certainly nicer than the ARM (which is otherwise not a bad core), or the 8051 (suggested by another poster), which would be a big step backwards from the 68008.

If you can see a ColdFire development kit or evaluation kit that matches your requirements, it's probably your best bet. There are a number of nice small integrated ColdFires that should work well.
.

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