Antminer S9 board - what the heck is PCAP

I first ran into this looking at the FSBL code. It is a facility that the ARM can use to load bitstreams into the PL fabric.

The TRM talks about it in connection with boot in section 6.4.3 (page 212). The PCAP is in the DevC. As near as I can tell, DevC is some Xilinx slang for the devcfg. See the TRM pages 1144 to 1166 for details on the devcfg registers.

The $99 dollar question is why the FSBL should have anything to do with loading bitstreams into the PL. In use cases I envision, the name of the game is to get the ARM booted up, then whatever code has been booted can load bitstreams. Two things are possible:

• Some use cases may run entirely in the PL
• Some applications may start more quickly if the FSBL loads a bitstream.