02-06-2012 10:26 PM
Readback function does what you want, unless the readback inhibit flag is set in the bitstream.
Have a nice synthesis
02-07-2012 06:28 PM
I am using impact 12.2 and the readback command is not present. I tried using version 9.1, and it had the readback command but I could not select it. When the bitstream was generated, it was done so with the -g readback flag enabled.
After doing some reading in the Virtex 4 user guide it seems that I would have to perform the readback using a custom FPGA/microcontroller implementation. I'm wondering if the same could be done with the USB platform cable and impact.
02-07-2012 11:09 PM
since the USB platform cable is driving the JTAG port, there should be no problem when using this.
In UG071 I found this little statement:
"There are two mandatory bitstream settings for readback: the BitGen security setting must
not prohibit readback (-g security:none), and bitstream encryption must not be used.
Additionally, if readback is to be performed through the SelectMAP interface, the port
must be set to retain its function after configuration by setting the persist option in BitGen
(-g Persist:Yes), otherwise the SelectMAP data pins revert to user I/O, precluding
further configuration operations. Beyond these security and encryption requirements, no
special considerations are necessary to enable readback through the Boundary-Scan port."
So it seems thet for V4 devices more than just -g ReadBack is needed.
Check the bitgen documentation for further details on the available options.
Have a nice synthesis
02-09-2012 03:13 PM
If you generate the bitstream with default bitgen option, this is documented with Austin's thread. Perform Verify and with the environment variable set correctly.
Note also that you'll not get back your configuration bitstream. There are active compoents like BRAM content that will likely be different, LUTRAM/SRL16 will be masked out, etc.
02-14-2012 03:56 PM
Ok. So here is what I'm trying to do: retreive bit file from FPGA and reprogram FPGA using retreived .bit file. I've read on some other posts that it's possible, but end result is never achieved. Here's what I've done so far:
1) Perform readback using "Verify" command in iMPACT
2) iMPACT dumps ISEimpact.bin file
3) Is it possible to program Virtex 4 FPGA using .bin file dumped by iMPACT?
All methods of programming seem to require either a .bit or .mcs file. If step 3 is not possible, is there a way to convert the .bin file into either a .bit file or a .mcs file?
02-14-2012 05:01 PM
Short answer. No, because you don't get the dynamic content back. (BRAM/LUTRAM/SRL16). In addition, Xilinx doesn't provide or support any public tool to convert a bin back to bit/mcs for reprogramming purpose.