A FIFO memory is a storage device that allows data to be written into and read from its array at independent data rates. The SN74ACT7804 is a 512-word by 18-bit FIFO for high speed and fast access times. It processes data at rates up to 50 MHz and access times of 15 ns in a bit-parallel format.

Data is written into memory on a low-to-high transition at the load-clock (LDCK) input and is read out on a low-to-high transition at the unload-clock (UNCK) input. The memory is full when the number of words clocked in exceeds the number of words clocked out by 512. When the memory is full, LDCK signals have no effect on the data residing in memory. When the memory is empty, UNCK signals have no effect.

Status of the FIFO memory is monitored by the full (FULL\), empty (EMPTY\), half-full (HF), and almost-full/almost-empty (AF/AE) flags.