checking Xilinx datasheet "UG585" (v1.12.1)
Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NAlistair Francis <alistair.francis@xilinx.com>
Message-Id: <20180208164818.7961-17-f4bug@amsat.org>