downloading with XMD ?

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Hi,

I'am wondering about the download capabilities of XMD.

If an FPGA is configured with impact on the JTAG, then software uses XMD
with the JTAG cable to be downloaded in FPGA.

If for example my SOC has a PPC, some BRAM, an OPB_EMC peripheral and some
externalSRAM attacheds to it.

Is XMD able to directely download my .elf into the external SRAM through the
EMC peripheral and launch software from the external SRAM ???

This is what I understand of the xilinx's webserver reference design to
work.
I'm not sure of this, I would thing there has to be a bootloader to
interface with XMD that will drive the EMC peripheral ???
But they don't speak about it...

Can someone clear this point ?
Thak you.

Stéphane.





Re: downloading with XMD ?

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Yes

The reset vector is at 0xfffffffc, so there has to be some memory to
vector the program off to where the rest of the memory is.

If you notice, from XMD, there are commands like mrd and mwr (memory
read) and (memory write) that are available via the JTAG emulator
through XMD.  One could write a tcl program that did a series of writes
and reads to load the program into memory.  There is a the "dow"
command available that takes an elf file and loads sram.  Others have
written tcl programs to program flash, which needs a series of mwr, mrd
commands.

- Hope this helps
Newman

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Re: downloading with XMD ?
Ok, thank you, it's getting clearer !

Stéphane.

snipped-for-privacy@f14g2000cwb.googlegroups.com...

sjulhes wrote:
Quoted text here. Click to load it
the

Yes

The reset vector is at 0xfffffffc, so there has to be some memory to
vector the program off to where the rest of the memory is.

If you notice, from XMD, there are commands like mrd and mwr (memory
read) and (memory write) that are available via the JTAG emulator
through XMD.  One could write a tcl program that did a series of writes
and reads to load the program into memory.  There is a the "dow"
command available that takes an elf file and loads sram.  Others have
written tcl programs to program flash, which needs a series of mwr, mrd
commands.

- Hope this helps
Newman

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Re: downloading with XMD ?
Just one more question.
In the FPGA what ressource realizes the physical external memory access ?
Is it the JTAG that drives the FPGA IO to creates access cycles ?
Is it the the use of the embedded hardware module which drives the EMC
peripheral ?
Something else ?

Thanks.

Stéphane.


snipped-for-privacy@f14g2000cwb.googlegroups.com...

sjulhes wrote:
Quoted text here. Click to load it
the

Yes

The reset vector is at 0xfffffffc, so there has to be some memory to
vector the program off to where the rest of the memory is.

If you notice, from XMD, there are commands like mrd and mwr (memory
read) and (memory write) that are available via the JTAG emulator
through XMD.  One could write a tcl program that did a series of writes
and reads to load the program into memory.  There is a the "dow"
command available that takes an elf file and loads sram.  Others have
written tcl programs to program flash, which needs a series of mwr, mrd
commands.

- Hope this helps
Newman

Quoted text here. Click to load it




Re: downloading with XMD ?
Newman,

  Do you know if it is possible to peek/poke the memory via XMD -  BRAM
or
cache memory (ultra-controller mode) without  halting the PPC?

I heard reading the BRAM can crorrupt it.

-Tony


Re: downloading with XMD ?

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 From Xilinx Answer 8181:

1. If Distributed RAMs or SRL16s are used in the design, reading back
those LUTs could destroy the contents within if the WE is asserted while
the readback is being performed on those frames.

2. The configuration logic takes over the address lines to the BRAMs, so
those RAMs cannot be accessed or written to while readback of the BRAM
frames is in progress.

IIRC, the BRAM contents themselves don't get trashed provided the WE is
not asserted, but any reads done by the user logic while a readback is
in progress have corrupted data.  In other words, you can't use the
bitstream readback while that BRAM is also being used by the PPC.  
However, the PPC is probably only using one port on the BRAM.  If that
is the case, you could add logic to read back the contents through the
second user port on the BRAM.


--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
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Re: downloading with XMD ?
Tony,
  Good question!  Unfortunately I do not have an answer.  In general,
poking may present a problem without some type of semaphore protection.
I've never used the cache memory in ultra-controller mode.  I've
observed some strange behavior when peeking memory when the PPC is
running.  I never was sure whether it was a limitation of the PPC jtag
emulation scheme, issues of the BRAM interconnect methodology employed,
or pilot error.

-Newman


Re: downloading with XMD ?
XMD uses the PPC to peek/poke the memory. In other words, XMD forces the
PPC to issue a PLB bus (or other interface) read/write operation. For
this to happen XMD first stops the PPC.

- Peter


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