User I/O via Altera MAX7000S JTAG?

Is there any way to use the JTAG pins of an EPM7128S for user I/O, without
permanently commiting them as I/O and thereby losing the JTAG capability? I
want to download data from the PC, via a ByteBlaster cable, into a 2kx8
static RAM connected to the CPLD. I suppose I could add some jumpers for
re-patching the 10-way header to standard I/O pins; or have a second,
dedicated header for the RAM download; but I would prefer to use the JTAG
pins if possible.

TIA

 

I believe that you can make the other pins of the CPLD go high and low via
the JTAG port. I don't have my Altera data book here. It will be very
slow.

You could bring a couple more connections to the JTAG connector by adding
a couple of pins and making it "non-standard" or comply with the "Holme
standard" if you prefer. You can then put one program into the CPLD to
load the static RAM and a different one to use it.

BTW: I routinely program 7000S parts with a cable that just uses
resistors and the parallel port of a PC. You don't need to specifically
use the Byteblaster cable to work with the Altera parts.

 

Thanks Ken. I probably won't need to fill more than 256 bytes of the RAM
and I don't mind if it takes a couple of seconds.

Does anyone know where I can find info on how to do this? I have the
"Altera ByteBlaster" device and the "Altera JTAG Server" service running on
Windows NT. Are the APIs documented? I also have Quartus II 4.1 Web
Edition installed.


Could someone Does anyone know how to do this?

 

sure someone knows!

there are many ways todo it, the most easy is possible to write a small JAM
(STAPL) program that will do what you need.
in case you are able able to use Delphi we also have and application that
reprograms parallel flash that is connected to several Altera PLDs that
could be a start point, hmm that code could serve as reference in any case?
hm I was about to upload this project to
http://gforge.openchip.org with sources but havent had time yet

antti

 

Google on "JAM" and "CPLD" you are likely to find stuff about the JAM
STAPL downloading method. Alter supports this and, at least, had
documentation about it. You can get the C source code.

On an NT system, doing direct printer port I/Os requires special drivers.
Even then the timing is a bit wobbly. If you have an old DOS machine, you
may be better off than with the NT machine. You can also do it under
Linux.

I think the 7000 series data sheet has a little about its ISP lines.

Basically, you shift in commands serially and it reacts to the command
words. For each thing you do, you shift in a clump of bits. While you
shift in, it also shifts results out. This is what the RDI and TDO lines
are all about.

You have to be careful to give the part clean signals.