Xilinx uses a microblaze for their DDR memory controller calibration as well. Initially they didn't, and I guess the calibration wouldn't always work. Softwar

Xilinx uses a microblaze for their DDR memory controller calibration as well. Initially they didn't, and I guess the calibration wouldn't always work. Software allows much more complicated algorithms for calibration than hard coded RTL state machines. I've used soft CPU's to act as the interface between hardware and user, usually over a UART.