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'[EE] JTAG'
2006\05\05@155106 by Mike Hord

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I thought JTAG was supposed to be easy and flexible.

I'm trying to find a cheap method for programming a
few different targets via JTAG:  Blackfin processors,
Xilinx CPLDs and FPGAs, and AVRs.  I'm having very
little luck with finding a single universal tool that can
be used to load code into any of these targets.

I'm only thinking about binary code, here.  No compilers,
no assemblers, nothing.  Just raw data that we wish to
place into the hardware.  Cheesy parallel port bitbangers
need not apply.

Google has not been my friend.

Mike H.

2006\05\05@191759 by Peter

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Mike Hord <mike.hord <at> gmail.com> writes:

> I thought JTAG was supposed to be easy and flexible.

Isn't it ?

> I'm trying to find a cheap method for programming a
> few different targets via JTAG:  Blackfin processors,
> Xilinx CPLDs and FPGAs, and AVRs.  I'm having very
> little luck with finding a single universal tool that can
> be used to load code into any of these targets.

In the context of JTAG, do you know of another hardware programming standard
that is cross platform (even as a pinout and voltage levels and timing) like
JTAG is ?

> I'm only thinking about binary code, here.  No compilers,
> no assemblers, nothing.  Just raw data that we wish to
> place into the hardware.  Cheesy parallel port bitbangers
> need not apply.

So it has to be cheap, not cheezy, and support products from many manufacturers
? Please share what you find.

> Google has not been my friend.

Google is very sick at the moment. It may not be its usual self.

Peter



2006\05\05@194514 by Peter

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> Google has not been my friend.

It is not so sick after all:

www.lauterbach.co.jp/frames.html?ord_bdm.html
www.pls-mc.com/deliveringsolutions/index.htm?a_debugger_ude.htm
http://microcontrollershop.com/product_info.php?products_id=938

Note that the latter uses a FTDI USB/serial chip internally, so it is not
'parallel', as you requested ;-)

Peter



2006\05\05@204039 by Mike Hord

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microcontrollershop.com/product_info.php?cPath=92&products_id=1325

Found this after much searching.  Almost must be an April Fool's joke- it's
just too perfect!  And at $199US, I can't afford NOT to get it!

Mike H.

PS- You're very right.  JTAG is delightfully simple.  It's really a matter of
either finding software support for your device or adequate documentation
to do what needs doing.  I suspect that with adequate time and documentation
any JTAG programmer would do what I need.  I just don't have either.

On 5/5/06, Peter <spam_OUTplpTakeThisOuTspamactcom.co.il> wrote:
{Quote hidden}

> -

2006\05\05@210746 by William Chops Westfield

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On May 5, 2006, at 5:40 PM, Mike Hord wrote:

> You're very right.  JTAG is delightfully simple.  It's really
> a matter of either finding software support for your device
> or adequate documentation to do what needs doing.

My impression is that JTAG gives you essentially a general purpose
interface for accessing bits inside a chip.  However, which bits
do what remains less specified, so to actually DO anything useful
to a chip, you get into less standard areas, moving all your problems
from the "device access device" to "host software."  In theory, that's
a good idea, since host software is "easier" to modify than device
programmer software, but in reality "easier" doesn't mean "easy", and
APIs to the JTAG device as well as details of the JTAG internals of
the target device can be less than well documented...

Does Jtag actually specify details for doing actual programming and
other high level functions?

BillW

2006\05\06@101730 by Peter

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On Fri, 5 May 2006, William Chops Westfield wrote:

> Does Jtag actually specify details for doing actual programming and
> other high level functions?

Afaik there are several standards for JTAG commands. The command sets
nest, forming an outer protocol and an inner protocol. The outer
protocol makes device interfaces compatible (f.ex. you can daisy-chain
JTAG devices and then address the relevant device from the end of the
chain). The inner protocols are debugging and testing protocols (what
JTAG was made for), and more recently programming protocols (which seem
to be proprietary). One has to read through the standards to discover
the details.

Peter

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