>Greetings all! I was an electronics hobbyist back in the late '70s
>and early '80s but have been pretty much a software guy since then. A
>few weeks back I stumbled onto the SX and was shocked that nowadays a
>50 MIPS microcontroller can be had for five bucks. I immediately went
>out and popped for the SX-tech tool kit. It should be arriving any
>day now.
>
>In the meantime, I've been researching other microcontrollers, mostly
>the Microchip PIC. I must say it has been quite an effort trying to
>figure out the product line, which chips are history, what to use
>where and so forth, but I'm beginning to see the method to the
>madness.
>
>I've found an incredible amount of information about the PICs on the
>web, perhaps almost too much. The number of different PIC programmers
>alone is astounding. And this is where I have my newbie question.
>I'm sure this is a FAQ, and if someone can point me to a single
>reference I'd be happy to go off and start reading. (Also, are
>archives of this list prior to the recent switch to majordomo
>available, and if so, where?)
>So, here's what I know (or think I know) and what I don't...
>
>It seems as if the only features the fancy (i.e. expensive)
>programmers have are the ability to program everything in a single
>socket and then test the programming at multiple voltage levels, but
>it also seems as if these features aren't really necessary for the
>hobbyist. It also seems as if they can program the older non-serial
>units, but I doubt I'd be dealing with any older chips at this point.
>The speed at which the chips are programmed seems to be more a
>function of the software than the programmer itself. Is there more
>that I'm missing here?
>
>It doesn't really seem as if the very simple programmers based on
>AN589 or COM84 really do anything different that the fancy-pants
>programmers, so long as you get the programming signals on the proper
>pins. The one difference I do see is that signal timing is handled by
>the PC, which on a slow machine (or perhaps even a not so slow
>machine) is non-deterministic in a multi-tasking environment.
>
>It seems as if the electrical characteristics of the AN589 circuit are
>standard for all recent PICs, and it is the software dataflow that
>really determines what chips can be programmed.
>
>Then there is the issue of in-circuit programming. It seems as if
>in-circuit programming uses the same programming functions and signals
>as the "standard" programming, and doing in-circuit programming is
>more a matter of designing the embedded circuit with proper isolation
>to accept in-circuit programming.
>
>Now, because I'm new to this, I'm going to be doing a lot of
>re-programming on a breadboard. (I even found my old breadboard and
>stash of old components!) It seems silly to constantly be moving the
>PIC back and forth between the breadboard and a programmer -- at the
>very least that would involve the purchase of two ZIF sockets. It
>would seem to make much more sense to wire the five programming pins
>from the breadboard to a socket which can then be plugged into either
>the programmer or a loopback to the breadboard. In reality, since I
>have just one rather large board, the programmer would likely live on
>the same breadboard to start out, epsecially if it was a simple one.
>The advantage of this "jumper" approach seems as if would simply
>eliminate the need for all of the isolation circuitry.
>
>This *seems* as if it would be a very simple and elegant solution to
>development and prototyping, yet I have found only a few references to
>this method. (Wisp and TLVP) Furthermore, it seems as if this method
>will easily allow the use of the LVP, eliminating the need for the 13v
>supply & associated circuitry. Are there issues involved that I am
>missing? Are there cases where this doesn't work?
>
>Right now, I'm leaning towards using Byron Jeff's design for the
>Trivial Parallel Port programmers (both the low voltage and high
>voltage varieties) due to the low component count. If this turns out
>to be a good solution, I'll probably use pp06 for programming because
>of it's wide device support. (That does mean I'll be writing my own
>parallel port driver, but given the modular nature of the program this
>seems trivial.) Again, this assumes the electrical characteristics
>for the different devices is the same, and it's the format of the data
>stream to the device that determines what devices can be programmed.
>
>I do have a specific project in mind which will require a fairly large
>number of simple PICs, and it looks like the 12F629/16F630 will fit
>that bill at $1.60/$1.80ea. (This is the specific reason for my
>interest in PIC instead of SX!) Although these devices are not billed
>as LVP devices, it seems as if they do not need the 13V of the more
>typical HVP devices. They seem to be HVP flash memory, but include an
>internal high voltage generator. It seems as if anything from 8.5V to
>13.5V will do the trick. If I'm understanding this correctly, it
>eliminates the need for that pesky 13V source!
>
>Many thanks in advance for any comments, advice and suggestions in
>these areas. Confirmation of where I'm right would be appreciated as
>well as note of where I'm in error!
>
>-p.
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