Virtex4+PPC+ext. RAM: Problems generating ACE files (solved!?)
- From: Torsten Landschoff <t.landschoff@xxxxxx>
- Date: Tue, 14 Aug 2007 03:44:02 -0700
Hi *,
[Warning: Long post, includes patch for genace.tcl]
I am working with a custom Virtex-4 based board design using an
internal
PowerPC core and external SDRAM for code and data. Using the standard
EDK
flow, all is well: I can download the bitstream, use the PPC JTAG
interface
to upload and debug the software application.
Now, for making my tests reproducible, I wanted to generate an ACE
file
containing both the FPGA and the software configuration. After going
through the documented steps to create an ACE file using genace.tcl,
the
resulting ACE file loaded fine. However, the software did not start
running.
Connecting with XMD revealed that the software was loaded correctly
both
into the SDRAM and the internal data memory. However, the instruction
memory - connected via an isbram_if_cntrl - was not correctly set up.
Which is unfortunate as the start vector points to that memory type.
I spent a lot of time with analyzing the situation. Maybe I am doing
something wrong but I am having trouble accessing the instruction
memory
from XMD even after having the system.xmp imported using
load xmp system.xmp
in xmd. It's just not working reliable. I tried loading the FPGA
design with
just the bootloop inside the BRAMs but was unable to see the branch
instruction doing the infinite loop. However, I could write new data
to
the instruction memory to jump into my application which then works
fine.
So I thought I had to mark my applicationt to initialize BRAMs in XPS.
This
solution leads to another problem: After configuration of the FPGA and
before
the System ACE controller load the application code to the SDRAM
memory, the
PowerPC inside the FPGA starts running and jumps into the
uninitialized
SDRAM.
As I was able to load the program correctly using xdm in interactive
mode,
I figured I could get it running by loading the system.xmp while
creating the
ACE file. This indeed helped, and my ACE files are now running fine.
What I did is a quick hack that works for me (tm), but I think this
should
be fixed in EDK as well. Here is the diff on genace.tcl:
--- /opt/Xilinx/EDK/data/xmd/genace.tcl 2006-06-30 03:26:56.000000000
+0200
+++ genace.tcl 2007-08-14 11:09:33.729977014 +0200
@@ -209,6 +209,11 @@
puts "Converting ELF file '$elffile' to SVF file '$svffile'"
set tgt 0
+
+ if { [catch { xload_sysfile xmp system.xmp } retval] } {
+ puts "$retval"
+ error "ERROR: Unable to load system.xmp"
+ }
if { $target_type == "ppc_hw" } {
set a "xconnect ppc hw -cable type xilinx_svffile fname
$svffile $xmd_options"
} else {
As I understand, the configuration flow now goes as follows:
- System is powered on / reset
- SysACE controller clears the FPGA configuration
- SysACE ctrl. waits for FPGA to get ready for conf
- SysACE downloads the logic and BRAM configuration to the Virtex4
- ### In an ideal world, the PPC would wait
until the software was downloaded ###
- instead: SysACE senses that FPGA is configured (DONE pin goes high),
PowerPC starts executing instructions (from BRAM)
- here: instruction BRAM just contains here: b here so PPC loops
- SysACE halts the PowerPC using JTAG, uploads program via JTAG
through the
PPC's memory interfaces (this is only done correctly if xmd had the
right
memory map while creating the svf file)
- SysACE sends "continue" command to PPC via JTAG
- Configuration is complete, PPC application up and running
Can somebody tell me if I got it right? Does the patch make sense or
is there
a better way to load instruction memory from System ACE? I tried using
xmd -xmp system.xmp -tcl genace.tcl -opt genace.opt
but it seems the "-xmp" option is ignored when running a script.
Hoping for a bit of feed back,
Torsten
.
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