This attribute defines the FIFO order when cascading FIFOs serially or sets the cascading to parallel. When cascading FIFOs in series, the first FIFO (the FIFO with the write interface) must have CASCADE_ORDER = "FIRST", the last FIFO (the FIFO with the read interface) must have CASCADE_ORDER = "LAST", and all other FIFOs in the chain must have CASCADE_ORDER = "MIDDLE". When expanding the FIFO in parallel mode, this attribute should be set to PARALLEL (see also Cascading FIFOs Serially and in Parallel to Extend Depth).
- NONE
- Normal FIFO operation.
- FIRST
- FIFO is the first in a series of FIFOs cascaded to extend depth. It has a normal write interface, but the read interface is modified to link with the next FIFO in the chain.
- MIDDLE
- FIFO is part of a chain of FIFOs cascaded to extend depth. It connects to the previous FIFO configured as FIRST or MIDDLE and connects to the next FIFO configured as MIDDLE or LAST.
- LAST
- FIFO is the last in a series of FIFOs cascaded to extend depth. It has a normal read interface, but the write interface is modified to link with the previous FIFO in the chain.
- PARALLEL
- FIFO is used in a design where the output data is cascaded in parallel.