Module axi_id_remap_table

Internal module of axi_id_remap: Table to remap input to output IDs.

This module contains a table indexed by the output ID (type idx_t). Each table entry has two

fields: the input ID and a counter that records how many transactions with the input and output

ID of the entry are in-flight.

The mapping from input and output IDs is injective. Therefore, when the table contains an entry

for an input ID with non-zero counter value, subsequent input IDs must use the same entry and

thus the same output ID.

Relation of types and table layout

diagram of table

Complexity

This module has:

MaxUniqInpIds * InpIdWidth * clog2(MaxTxnsPerId) flip flops;
MaxUniqInpIds comparators of width InpIdWidth;
2 leading-zero counters of width MaxUniqInpIds.

Parameters

`InpIdWidth: int unsigned`

Width of input IDs, therefore width of id_inp_t.

`MaxUniqInpIds: int unsigned`

Maximum number of different input IDs that can be in-flight. This defines the number of remap

table entries.

The maximum value of this parameter is 2**InpIdWidth.

`MaxTxnsPerId: int unsigned`

Maximum number of in-flight transactions with the same ID.

`id_inp_t: type`

Derived (=do not override) type of input IDs.

`IdxWidth: int unsigned`

Derived (=do not override) width of table index (ceiled binary logarithm of

MaxUniqInpIds).

`idx_t: type`

Derived (=do not override) type of table index (width = IdxWidth).

`field_t: type`

Derived (=do not override) type with one bit per table entry (thus also output ID).

`CntWidth: int unsigned`

Counter width, derived to hold numbers up to MaxTxnsPerId.

Ports

`clk_i: input logic`

Rising-edge clock of all ports

`rst_ni: input logic`

Asynchronous reset, active low

`free_o: output field_t`

One bit per table entry / output ID that indicates whether the entry is free.

`free_oup_id_o: output idx_t`

Lowest free output ID. Only valid if the table is not full (i.e., !full_o).

`full_o: output logic`

Indicates whether the table is full.

`push_i: input logic`

Push an input/output ID pair to the table.

`push_inp_id_i: input id_inp_t`

Input ID to be pushed. If the table already contains this ID, its counter must be smaller than

MaxTxnsPerId.

`push_oup_id_i: input idx_t`

Output ID to be pushed. If the table already contains the input ID to be pushed, the output

ID must match the output ID of the existing entry with the same input ID.

`exists_inp_id_i: input id_inp_t`

Input ID to look up in the table.

`exists_o: output logic`

Indicates whether the given input ID exists in the table.

`exists_oup_id_o: output idx_t`

The output ID of the given input ID. Only valid if the input ID exists (i.e., exists_o).

`exists_full_o: output logic`

Indicates whether the maximum number of transactions for the given input ID is reached. Only

valid if the input ID exists (i.e., exists_o).

`pop_i: input logic`

Pop an output ID from the table. This reduces the counter for the table index given in

pop_oup_id_i by one.

`pop_oup_id_i: input idx_t`

Output ID to be popped. The counter for this ID must be larger than 0.

`pop_inp_id_o: output id_inp_t`

Input ID corresponding to the popped output ID.

Types

cnt_t	Counter that tracks the number of in-flight transactions with an ID.
entry_t	Type of a table entry.