gigabee B2B configuration

[rifo]

Hello,

I am trying to design a headerboard where a gigabee and a dsp module are to be connected. I planned on using slave serial method for configuring the FPGA via DSP but as far as I see, "Din" signal is missing in the connectors. In LX100, "Din" signal belongs to Bank2 and has the pin number AA20. This corresponds to L3_P in bank 2.
I would be happy if someone can confirm this.

thanks for your time
rifo

[Thorsten Trenz]

Hi,
GigaBee is not designed to be configured with slave serial mode. It is fixed to SPI. There is no way to set other modes.

best regards
Thorsten Trenz

[rifo]

Okey I think I misunderstood the user guide where it says FPGA configuration through B2B connector is possible.

Should I then program the flash memory (via SPI) with the DSP? If yes, doesn't this cause 2 masters on the SPI bus (DSP and FPGA) One more possible problem is that if the DSP can't  3 state the SPI flash slave select signal wouldn't there be a problem?
Anyway these questions are of course based on my assumption that DSP should program the SPI flash in order to configure the FPGA. Can you please guide me further on this issue?

thank you very much for your help
best regards
rifo

[Thorsten Trenz]

Hi,
when your DSP programs the SPI Flash, you have to hold the FPGA in Reset, by pulling the Prog_B line Low.
The DSP definitely needs to tristate the SPI Bus during FPGA boot and FPGA access.

I assume you need different FPGA configurations, because you want to program it from DSP? If not, it is enough to programm the SPI Flash one time with a JTAG adapter.

If you need only a few, please read the Spartan-6 Configuration User Guide for Multiboot.

best regards
Thorsten Trenz

[rifo]

Hello Thorsten,

Thanks a lot for your answer. What I had in mind was to remotely update the FPGA configuration (through the DSP and internet) at some point. I guess I can use a CPLD for tristating the SPI bus but fortunately this is not something urgent so I can just omit it for quite some time. I will configure the FPGA flash with JTAG. Can I then assume that on the DSP side, I simply don't have to do anything with FPGA configuration pins.

thank you very much for your time
rifo

[Thorsten Trenz]

Hi Rifo,
if you do not connect the SPI Pins, then you are fine.

best regards
Thorsten Trenz