The PicoBlaze or the KCPSM3 named after its inventor Ken Chapman, System designer at Xilinx.
The PSM stands for Programmable State Machine - The source code can be downloaded for free from Xilinx website
The source code defined at a rather low level VHDL, which gives a very efficient utilization of the FPGA structure but also makes it very hard to understand for an interested designer.
 

 The machine code for a KCPSM3 will use one BlockRAM / ROM and its possible to create a design where the code can be loaded directly to the BRAM via the JTAG interface.