Entity fifo_cc_got_tempgot

Block Diagram of fifo_cc_got_tempgot

The specified depth (MIN_DEPTH) is rounded up to the next suitable value.

As uncommitted reads occupy FIFO space that is not yet available for writing, an instance of this FIFO can, indeed, report full and not vld at the same time. While a commit would eventually make space available for writing (not ful), a rollback would re-iterate data for reading (vld).

commit and rollback are inclusive and apply to all reads (got) since the previous commit or rollback up to and including a potentially simultaneous read.

The FIFO state upon a simultaneous assertion of commit and rollback is undefined!

*STATE_*_BITS defines the granularity of the fill state indicator *state_*. fstate_rd is associated with the read clock domain and outputs the guaranteed number of words available in the FIFO. estate_wr is associated with the write clock domain and outputs the number of words that is guaranteed to be accepted by the FIFO without a capacity overflow. Note that both these indicators cannot replace the full or valid outputs as they may be implemented as giving pessimistic bounds that are minimally off the true fill state.

If a fill state is not of interest, set *STATE_*_BITS = 0.

fstate_rd and estate_wr are combinatorial outputs and include an address comparator (subtractor) in their path.

Examples:

• FSTATE_RD_BITS = 1:

  • fstate_rd == 0 => 0/2 full

  • fstate_rd == 1 => 1/2 full (half full)

• FSTATE_RD_BITS = 2:

  • fstate_rd == 0 => 0/4 full

  • fstate_rd == 1 => 1/4 full

  • fstate_rd == 2 => 2/4 full

  • fstate_rd == 3 => 3/4 full

Generics

Name	Type	Default	Description
D_BITS	positive		Data Width
MIN_DEPTH	positive		Minimum FIFO Depth
DATA_REG	boolean	false	Store Data Content in Registers
STATE_REG	boolean	false	Registered Full/Empty Indicators
OUTPUT_REG	boolean	false	Registered FIFO Output
ESTATE_WR_BITS	natural	0	Empty State Bits
FSTATE_RD_BITS	natural	0	Full State Bits

Ports

Name	Type	Direction	Description
rst	std_logic	in	Global Reset and Clock
clk	std_logic	in
put	std_logic	in	Writing Interface Write Request
din	std_logic_vector	in	Input Data
full	std_logic	out
estate_wr	std_logic_vector	out
got	std_logic	in	Reading Interface Read Completed
dout	std_logic_vector	out	Output Data
valid	std_logic	out
fstate_rd	std_logic_vector	out
commit	std_logic	in
rollback	std_logic	in

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