Authors:	Filip Hofer
	Jan Korenek

UH FIFO is memory organised as FIFO which contain Unified Headers (UH) generated by HFE processor. It has 16 items and is organised as circular buffer. LUP reads UH and performs classification. When UH processing is finished, it is released.

Unified Header FIFO

Unified-header is physically stored in a buffer. The buffer is filled by the Header Field Extractor and read by the look-up processor. The read and write operations have to be fully independent. Therefore the buffer is stored in dual port Block SelectRAM in the FPGA chip.

The buffer consists of 16 items, each containing a Unified header (UH). The buffer is controlled by a status register; one bit for one set of registers. The bit signalizes whether the item is free or contains a UH. Header field extractor can write a UH to the item only if the bit is zero. When the UH is fully written to the buffer, the bit is set. The buffer is read by the look-up processor. It can start handling the UH only if the bit is set. When it finishes the work it resets the bit. This way we guarantee that the header field extractor never rewrites any stored UH and the look-up processor never processes the UH that has not been fully stored.