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JTAG tutorial

Started by Jean Nicolle May 12, 2006
I created a small tutorial about JTAG.
See http://www.fpga4fun.com/JTAG.html

I'd be happy to hear about mistakes/suggestions.
Thanks. 


>I created a small tutorial about JTAG...
http://www.fpga4fun.com/JTAG.html
> >...happy to hear about mistakes/suggestions...
I haven't read it in detail, so I won't comment on the content, but I like the style. It's well-paced. It's concise. It doesn't have unnecessary and confusing repetition. It's laid out clearly with good diagrams. Most articles fail on all these points. I'd only say that it's best to avoid writing small numbers (1-10) and non-exact numbers as digits. E.g. it's easier to read "a few thousand...three inputs and one output" than "a few 1000...3 inputs, and 1 output". Mike
On a sunny day (Fri, 12 May 2006 04:08:46 GMT) it happened "Jean Nicolle"
<jean.nicolle@sbcglobal.net> wrote in
<iTT8g.69949$_S7.49845@newssvr14.news.prodigy.com>:

>I created a small tutorial about JTAG. >See http://www.fpga4fun.com/JTAG.html
Very nice! Just learned a bit more about JTAG.
Jean Nicolle wrote:
> I created a small tutorial about JTAG. > See http://www.fpga4fun.com/JTAG.html > > I'd be happy to hear about mistakes/suggestions. > Thanks. > >
You mentioned that some external Flash manufacuturers make versions that can be ISP via JTAG? I have been looking for such a Chip! Do you know of any off hand? Most are programmed through the SPI or Parrallel interface, it woulds be nice to have some JTAG capable for faster debug. Thanks, ELi
Eli

most flash devices do not have a JTAG port but can still be programmed
via JTAG by ensuring all the pins of the flash chip which are required
address, data, and control signals are connected to a device which does
have a boundary scan port. Unused fpag pins are good for this. The JTAG
software can then control the FPGA pins connected to the flash to write
data into the flash device. If you are going to do it this way it is
often necessary to take the WE pin to a spare pin on the JTAG header to
enable the speed of the programming to be quicker.

hope this helps

Ad

Thanks!

Ok, I fixed a few instances of the numbers.

<MikeShepherd564@btinternet.com> wrote in message 
news:eud862pue2p4m6u274up9jj7qhp8si0ena@4ax.com...
> >I created a small tutorial about JTAG... > http://www.fpga4fun.com/JTAG.html >> >>...happy to hear about mistakes/suggestions... > > I haven't read it in detail, so I won't comment on the content, but I > like the style. It's well-paced. It's concise. It doesn't have > unnecessary and confusing repetition. It's laid out clearly with good > diagrams. Most articles fail on all these points. > > I'd only say that it's best to avoid writing small numbers (1-10) and > non-exact numbers as digits. E.g. it's easier to read "a few > thousand...three inputs and one output" than "a few 1000...3 inputs, > and 1 output". > > Mike
Correct.

I actually know only one flash that can be programmed through JTAG (Platform 
flash, made by ST, sold by Xilinx). So I'm a little optimistic in my 
webpage.
Anyone knows if we can get these flash from ST directly? or another source?

"Ad" <adam.taylor@eads.com> wrote in message 
news:1147441764.754114.86100@d71g2000cwd.googlegroups.com...
> Eli > > most flash devices do not have a JTAG port but can still be programmed > via JTAG by ensuring all the pins of the flash chip which are required > address, data, and control signals are connected to a device which does > have a boundary scan port. Unused fpag pins are good for this. The JTAG > software can then control the FPGA pins connected to the flash to write > data into the flash device. If you are going to do it this way it is > often necessary to take the WE pin to a spare pin on the JTAG header to > enable the speed of the programming to be quicker. > > hope this helps > > Ad >
GREAT LINK.  I typically check your website and have used your forums a few 
times.  In fact I asked a question about the JTAG stuff a while ago.  I have 
compiled and tried playing around with your examples with a 4 device board I 
designed.  I am going to try writing my own C app to test my boards.  Your 
site is just what I was looking for.

Anyone know of other C tutorials for writing your own JTAG apps?  I would 
rather write my own than buy the really expensive commercial applications.

matt




"Jean Nicolle" <jean.nicolle@sbcglobal.net> wrote in message 
news:Um59g.4988$fb2.2761@newssvr27.news.prodigy.net...
> Correct. > > I actually know only one flash that can be programmed through JTAG > (Platform flash, made by ST, sold by Xilinx). So I'm a little optimistic > in my webpage. > Anyone knows if we can get these flash from ST directly? or another > source? > > "Ad" <adam.taylor@eads.com> wrote in message > news:1147441764.754114.86100@d71g2000cwd.googlegroups.com... >> Eli >> >> most flash devices do not have a JTAG port but can still be programmed >> via JTAG by ensuring all the pins of the flash chip which are required >> address, data, and control signals are connected to a device which does >> have a boundary scan port. Unused fpag pins are good for this. The JTAG >> software can then control the FPGA pins connected to the flash to write >> data into the flash device. If you are going to do it this way it is >> often necessary to take the WE pin to a spare pin on the JTAG header to >> enable the speed of the programming to be quicker. >> >> hope this helps >> >> Ad >> > >