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Common Cells Repository

Maintainer: Florian Zaruba zarubaf@iis.ee.ethz.ch

This repository contains commonly used cells and headers for use in various projects.

Cell Contents

This repository currently contains the following cells, ordered by categories. Please note that cells with status deprecated are not to be used for new designs and only serve to provide compatibility with old code.

Clocks and Resets

Name Description Status Superseded By
clk_div Clock divider with integer divisor active
clock_divider Clock divider with configuration registers deprecated clk_div
clock_divider_counter Clock divider using a counter deprecated clk_div
rstgen Reset synchronizer active
rstgen_bypass Reset synchronizer with dedicated test reset bypass active

Clock Domains and Asynchronous Crossings

Name Description Status Superseded By
cdc_2phase Clock domain crossing using two-phase handshake, with ready/valid interface active
cdc_fifo_2phase Clock domain crossing FIFO using two-phase handshake, with ready/valid interface active
cdc_fifo_gray Clock domain crossing FIFO using a gray-counter, with ready/valid interface active
edge_detect Rising/falling edge detector active
edge_propagator ANTONIO ADD DESCRIPTION active
edge_propagator_rx ANTONIO ADD DESCRIPTION active
edge_propagator_tx ANTONIO ADD DESCRIPTION active
pulp_sync Serial line synchronizer deprecated sync
pulp_sync_wedge Serial line synchronizer with edge detector deprecated sync_wedge
serial_deglitch Serial line deglitcher active
sync Serial line synchronizer active
sync_wedge Serial line synchronizer with edge detector active

Counters and Shift Registers

Name Description Status Superseded By
counter Generic up/down counter with overflow detection active
delta_counter Up/down counter with variable delta and overflow detection active
generic_LFSR_8bit 8-bit linear feedback shift register (LFSR) deprecated lfsr_8bit
lfsr_8bit 8-bit linear feedback shift register (LFSR) active
lfsr_16bit 16-bit linear feedback shift register (LFSR) active
lfsr 4...64-bit parametric Galois LFSR with optional whitening feature active
max_counter Up/down counter with variable delta that tracks its maximum value active
mv_filter ZARUBAF ADD DESCRIPTION active

Data Path Elements

Name Description Status Superseded By
addr_decode Address map decoder active
binary_to_gray Binary to gray code converter active
find_first_one Leading-one finder / leading-zero counter deprecated lzc
gray_to_binary Gray code to binary converter active
lzc Leading/trailing-zero counter active
onehot_to_bin One-hot to binary converter active
shift_reg Shift register for arbitrary types active
rr_arb_tree Round-robin arbiter for req/gnt and vld/rdy interfaces with optional priority active
rrarbiter Round-robin arbiter for req/ack interface with look-ahead deprecated rr_arb_tree
prioarbiter Priority arbiter arbiter for req/ack interface with look-ahead deprecated rr_arb_tree
fall_through_register Fall-through register with ready/valid interface active
spill_register Register with ready/valid interface to cut all combinational interface paths active
stream_arbiter Round-robin arbiter for ready/valid stream interface active
stream_arbiter_flushable Round-robin arbiter for ready/valid stream interface and flush functionality active
stream_demux Ready/valid interface demultiplexer active
stream_mux Ready/valid interface multiplexer active
stream_register Register with ready/valid interface active
stream_fork Ready/valid fork active
stream_filter Ready/valid filter active
stream_delay Randomize or delay ready/valid interface active
sub_per_hash Substitution-permutation hash function active
popcount Combinatorial popcount (hamming weight) active

Data Structures

Name Description Status Superseded By
cb_filter Counting-Bloom-Filter with combinational lookup active
fifo FIFO register with upper threshold deprecated fifo_v3
fifo_v2 FIFO register with upper and lower threshold deprecated fifo_v3
fifo_v3 FIFO register with generic fill counts active
generic_fifo FIFO register without thresholds deprecated fifo_v3
generic_fifo_adv FIFO register without thresholds deprecated fifo_v3
sram SRAM behavioral model active
plru_tree Pseudo least recently used tree active
unread Empty module to sink unconnected outputs into active

Header Contents

This repository currently contains the following header files.

RTL Register Macros

The header file registers.svh contains macros that expand to descriptions of registers. To avoid misuse of always_ff blocks, only the following macros shall be used to describe sequential behavior. The use of linter rules that flag explicit uses of always_ff in source code is encouraged.

Macro Arguments Description
`FF q_sig, d_sig, rst_val Flip-flop with asynchronous active-low reset (implicit)
`FFAR q_sig, d_sig, rst_val, clk_sig, arst_sig Flip-flop with asynchronous active-high reset
`FFARN q_sig, d_sig, rst_val, clk_sig, arstn_sig Flip-flop with asynchronous active-low reset
`FFSR q_sig, d_sig, rst_val, clk_sig, rst_sig Flip-flop with synchronous active-high reset
`FFSRN q_sig, d_sig, rst_val, clk_sig, rstn_sig Flip-flop with synchronous active-low reset
`FFNR q_sig, d_sig, clk_sig Flip-flop without reset
`FFL q_sig, d_sig, load_ena, rst_val Flip-flop with load-enable and asynchronous active-low reset (implicit)
`FFLAR q_sig, d_sig, load_ena, rst_val, clk_sig, arst_sig Flip-flop with load-enable and asynchronous active-high reset
`FFLARN q_sig, d_sig, load_ena, rst_val, clk_sig, arstn_sig Flip-flop with load-enable and asynchronous active-low reset
`FFLSR q_sig, d_sig, load_ena, rst_val, clk_sig, rst_sig Flip-flop with load-enable and synchronous active-high reset
`FFLSRN q_sig, d_sig, load_ena, rst_val, clk_sig, rstn_sig Flip-flop with load-enable and synchronous active-low reset
`FFLNR q_sig, d_sig, load_ena, clk_sig Flip-flop with load-enable without reset
  • The name of the clock and reset signals for implicit variants is clk_i and rst_ni, respectively.
  • Argument suffix _sig indicates signal names for present and next state as well as clocks and resets.
  • Argument rst_val specifies the value literal to be assigned upon reset.
  • Argument load_ena specifies the boolean expression that forms the load enable of the register.