"Jon Dohnson" <jon_dohnson@nothanks.usenet.only.com> wrote in message
news:pan.2004.11.29.16.58.04.220000@nothanks.usenet.only.com...
> I have  a couple of questions about the board layout of the spartan3 and
> platform flash. In the spartan-3 family guide there is a schematic for
> programming the spartan-3 from a platform flash on page 33. To put the
> spartan 3 in master serial mode you need M0-M2 (mode pins) as 000. In
> theory the spartan-3 and platform flash should step through the flow chart
> of boot up mode.
>
> Do I need to then change the mode pins, or is it okay to leave them
> hardwired to GND ?
OK

> My second question is about JTAG. In order to make this in-system
> programmable I would of course like to use my JTAG port just like on the
> sp-3 starter kit. Do I need to do anything in particular to the mode pins,
> M0-M2, at this point or does JTAG override them so that I can then
> program up the platform flash just like I do with the starter kit?

nothing special

> I had always thought the JTAG would be dominant (using IMPACT) but this
> isn't something I want to leave to chance, as prototype boards aren't
> cheap when you aren't doing them yourself.

it is. JTAG is useable no matter the mode pins, just make sure the PROG is
not pulled up correctly, things like that

on good advice, look at xilinx, there is an appnote how todo read access to
platform flash after config, if that woule be desired you need on more
additional connection to platform flash

antti

I have  a couple of questions about the board layout of the spartan3 and
platform flash. In the spartan-3 family guide there is a schematic for
programming the spartan-3 from a platform flash on page 33. To put the
spartan 3 in master serial mode you need M0-M2 (mode pins) as 000. In
theory the spartan-3 and platform flash should step through the flow chart
of boot up mode.

Do I need to then change the mode pins, or is it okay to leave them
hardwired to GND ?

My second question is about JTAG. In order to make this in-system
programmable I would of course like to use my JTAG port just like on the
sp-3 starter kit. Do I need to do anything in particular to the mode pins,
M0-M2, at this point or does JTAG override them so that I can then 
program up the platform flash just like I do with the starter kit?

I had always thought the JTAG would be dominant (using IMPACT) but this
isn't something I want to leave to chance, as prototype boards aren't
cheap when you aren't doing them yourself.

Thanks very much for your time.