Xilinx notes

To simplify further explanations, we consider the project is generated in the current directory.


  1. Spartan Edge Accelerator Board has only pinheader, so the cable must be provided

  2. A JTAG <-> SPI bridge (used to write bitstream in FLASH) is available for some device, see spiOverJtag to check if your model is supported.

  3. Board provides the device/package model, but if the targeted board is not officially supported but the FPGA yes, you can use --fpga-part to provide the model.

  4. With spartan3, the flash is an independent JTAG device. User has to use --index-chain to access FPGA (RAM only) or flash (write/read only).


*.bin may be loaded in memory or in flash, but this extension is a classic extension for CPU firmware and, by default, openFPGALoader loads file in memory. Double check -m / -f when you want to use a firmware for a softcore (or anything, other than a bitstream) to write somewhere in the FLASH device).

.bit file is the default format generated by vivado, so nothing special task must be done to generate this bitstream.

.bin is not, by default, produced. To have access to this file you need to configure the tool:

  • GUI: Tools -> Settings -> Bitstreams -> check -bin_file.

  • TCL: append your TCL file with set_property STEPS.WRITE_BITSTREAM.ARGS.BIN_FILE true [get_runs impl_1].


For alchitry board the bitstream must be configured with a buswidth of 1 or 2. Quad mode can’t be used with alchitry’s FLASH.


For boards based on a Zynq (7000 or MPSoC), boot mode must be configured for JTAG (for Zedboard JP7->JP11 must be to GND).

Loading a bitstream

.bit and .bin are allowed to be loaded in memory.

File load:

openFPGALoader [-m] -b arty *.runs/impl_1/*.bit (or *.bin)


openFPGALoader [-m] -b spartanEdgeAccelBoard -c digilent_hs2 *.runs/impl_1/*.bit (or *.bin)

SPI flash


.bit, .bin, and .mcs are supported for FLASH.

.mcs must be generated through Vivado with a tcl script like:


For boards based on Zynq device (7000 and MPSoC) SPI flash is not accessible through PL.

set project [lindex $argv 0]

set bitfile "${project}.runs/impl_1/${project}.bit"
set mcsfile "${project}.runs/impl_1/${project}.mcs"

write_cfgmem -format mcs -interface spix4 -size 16 \
   -loadbit "up 0x0 $bitfile" -loaddata "" \
   -file $mcsfile -force


-interface spix4 and -size 16 depends on SPI flash capability and size.

The tcl script is used with:

vivado -nolog -nojournal -mode batch -source script.tcl -tclargs myproject

File load:

openFPGALoader [--fpga-part xxxx] -f -b arty *.runs/impl_1/*.mcs (or .bit / .bin)


-f is required to write bitstream (without them .bit and .bin are loaded in memory).


--fpga-part is only required if this information is not provided at board.hpp level or if the board is not officially supported. device/package format is something like xc7a35tcsg324 (arty model). See src/board.hpp, or spiOverJtag directory for examples.

Some boards with UltraScale FPGAs, like the VCU118 and KCU16, support the SPIx8 (Dual Quad SPI) configuration. In this case, the spix8 option write_cfgmem on the above example can be used to generate two .mcs files, to fit bigger designs or for faster programming. Only .mcs files can be used to program the FPGA in this case.

In this case, to load the two .mcs files:

openFPGALoader --board vcu118 -f --target-flash both --bitstream *.runs/impl_1/*_primary.mcs --secondary-bitstream *.runs/impl_1/*_secondary.mcs

On these boards, each SPI flash can be programmed independently with the --target-flash option. The default target is the primary flash.

For example, to program only the secondary flash with arbitrary data not related to FPGA configuration:

openFPGALoader --board vcu118 -f --target-flash secondary --bitstream arbitrary_data