Re: Carte Blanche JTAG cable questions

[Steve <srkh28@gmail.com>]

There is more info here if it helps;

http://www.applelogic.org/ProgrammingCBsFPGA.html

There are several area's on the site that talk about JTAG, but not
specifically. Ill add more info that covers these questions here.

steve

On Oct 7, 5:33 pm, Alex Freed <alex_n...@mirrow.com> wrote:
> Steven Hirsch wrote:
>
> >> Do I connect to the Digilent cable to the SOFT or the HARD pins or both?
>
> > Definitely not both.  I believe it would be the HARD set, but don't take
> > my word for it!  I'd much like Alex or Steve to explain the distinction
> > and uses of hard vs. soft JTAG.
>
> Correct. The "hard" JTAG is the real JTAG. The "soft" JTAG is used by
> Altium Designer tools to talk to soft instruments inside the FPGA. As we
> are not currently using AD, the "soft JTAG" pins are free for other use.
> The default configuration uses two as 3.3V level serial port. NOT to be
> connected to RS232 which is +/-12V.
>
>
>
> >> Also the CB schematic shows the CONNECT pin as VREF (whatever that
> >> is).  It also says "IF YOU ARE CONNECTING THIS INTERFACE TO USER BOARD
> >> A OR USER BOARD B DO NOT CONNECT THE REF PIN. REFER TO THE APPLELOGIC
> >> WEBSITE FOR DETAILS".  Unfortunately, the Applelogic website seems to
> >> be down.  So before I fry my CB card can anyone give me a heads-up on
> >> what to do?
>
> > That's definitely a Steve-or-Alex question...
>
> The JTAG connector on the CB was designed to be AD compatible. The
> CONNECT pin is used to let the rest of the system know that something is
> plugged in. This is not needed using non-Altium tools but other cables
> require a voltage reference. Note that Digilent cable says something
> like "1.8 to 5V". It needs to know which voltage to use. The VREF is
> used for that. So CB design was modified to rewire the unneeded CONNECT
> as a voltage reference for the non-Altium JTAG cables.
>
> -Alex.