VHDL: First Word Fall Through FIFO

In the Standard FIFO post I talked about how a traditional FIFO works and supplied code for one. In this post I will be describing a First Word Fall Through (FWFT) FIFO. The main difference between standard FIFOs and FWFT FIFOs are that, as the name describes, the first byte written into the FIFO immediately appears on the output (See image below). This allows the first byte to be read on the next clock cycle without having to strobe the read enable. Additionally you can read the byte and strobe the write enable high at the same time so the next byte will be available to read on the next clock cycle.
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VHDL: Standard FIFO

FIFOs (First In, First Out) are essentially memory buffers used to temporarily store data until another process is ready to read it. As their name suggests the first byte written into a FIFO will be the first one to appear on the output. Typically FIFOs are used when you have two processes that operate and a different rate. A common example is a high speed communications channel that writes a burst of data into a FIFO and then a slower communications channel that read the data as need to send it at a slower rate.

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