Question: - What should pin XOn, /XO, RXOn, /RXO, RXIn, /RXI, WXOn, /WXO, WXIn, /WXI, FLn, /FL be tied to if I am not cascading? - What should these pins be tied to if I am width cascading? - What should these pins be tied to if I am depth cascading?
Answer: The usage of these pins will vary depending on how you are using the FIFO. The possible ways a FIFO can be used are in width expansion (making a wider FIFO by using two or more FIFOs together), depth expansion (making a deeper FIFO by using two or more FIFOs together), or in standalone operation. Below is a listing of the different ways to set up your FIFO:
Standalone-
XO# (RXO# or WXO#) can be left floating
XI# (RXI# or WXI#) should be tied to Vss (ground)
FL#/RT can be tied to Vss (ground) and RT can be strobed to use the Retransmit feature
Width Expansion-
Same as standalone but RT will not work
Depth Expansion-
XO# (RXO# or WXO#) of the first FIFO should be connected to XI# (RXI# or WXI#) of the second FIFO. XO# of the second FIFO should be connected to XI# of the third FIFO and so on. XO# of the last FIFO should then be connected to XI# of the first FIFO, completing the chain.
FL#/RT of the first FIFO should be tied to Vss (ground). All other FIFOs down the chain should have FL#/RT tied to Vcc.
