The Spartan-3A Configuration User Guide describes a configuration flow for configuring multiple devices where the first device is in BPI mode and the rest of the devices are in slave serial mode. This method will create a serial daisy chain after the first device is in BPI mode.
How is this implemented in software?
The first bitfile will need to have the following BitGen option set, and then the files are built in iMPACT using the GUI to map out the daisy chain.
- g bpi_div8:yes
To generate the PROM files, the -bpi_dc <serial/parallel> flag will need to be set to enable PROMGen to include the correct command set for the first device. When the downstream chain is a serial chain, use the serial setting.
All other options in the software tools can be left as default or modified as specified in the requirements of the system.