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Superseded By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_int_div
Arbitrary integer clock divider with config interface and 50% output clock duty cycle
active
clk_int_div_static
A convenience wrapper around clk_int_div with static division factor.
active
clk_div
Clock divider with integer divisor
deprecated
clk_int_div
clock_divider
Clock divider with configuration registers
deprecated
clk_int_div
clock_divider_counter
Clock divider using a counter
deprecated
clk_int_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Superseded By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_4phase
Clock domain crossing using 4-phase handshake, with ready/valid interface
active
cdc_2phase
Clock domain crossing using two-phase handshake, with ready/valid interface
active
cdc_2phase_clearable
Identical to cdc_2phase but supports one-sided async/sync resetting of either src or dst
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
cdc_fifo_gray_clearable
Identical to cdc_fifo_gray but supports one-sided async/sync resetting of either src or dst
active
cdc_reset_ctrlr
Lock-step reset sequencer accross clock domains (internally used by clearable CDCs)
active
clk_mux_glitch_free
A glitch-free clock multiplexer with parametrizeable number of inputs.
active
edge_detect
Rising/falling edge detector
active
edge_propagator
Propagates a single-cycle pulse across an asynchronous clock domain crossing
active
edge_propagator_ack
edge_propagator with sender-synchronous acknowledge pin (flags received pulse)
active
edge_propagator_rx
Receive slice of edge_propagator, requires only the receiver clock
active
edge_propagator_tx
Transmit slice of edge_propagator, requires only the sender clock
active
isochronous_spill_register
Isochronous clock domain crossing and full handshake (like spill_register)
active
isochronous_4phase_handshake
Isochronous four-phase handshake.
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
addr_decode_dync
Address map decoder extended to support dynamic online configuration
active
addr_decode_napot
Address map decoder using naturally-aligned power of two (NAPOT) regions
active
multiaddr_decode
Address map decoder using NAPOT regions and allowing for multiple address inputs
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_flushable
Register with ready/valid interface to cut all combinational interface paths and additional flush signal.
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
lossy_valid_to_stream
Convert Valid-only to ready/valid by updating in-flight transaction
active
stream_join
Ready/valid handshake join multiple to one common
active
stream_join_dynamic
Ready/valid handshake join multiple to one common, dynamically configurable subset selection
active
stream_mux
Ready/valid interface multiplexer
active
stream_register
Register with ready/valid interface
active
stream_fork
Ready/valid fork
active
stream_fork_dynamic
Ready/valid fork, with selection mask for partial forking
active
stream_filter
Ready/valid filter
active
stream_delay
Randomize or delay ready/valid interface
active
stream_to_mem
Use memories without flow control for output data in streams.
active
stream_xbar
Fully connected crossbar with ready/valid interface.
active
stream_omega_net
One-way stream omega-net with ready/valid interface. Isomorphic to a butterfly.
active
stream_throttle
Restrict the number of outstanding transfers in a stream.
active
sub_per_hash
Substitution-permutation hash function
active
popcount
Combinatorial popcount (hamming weight)
active
mem_to_banks_detailed
Split memory access over multiple parallel banks with detailed response signals
active
mem_to_banks
Split memory access over multiple parallel banks
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
stream_fifo
FIFO register with ready/valid interface
active
stream_fifo_optimal_wrap
Wrapper that optimally selects either a spill register or a FIFO
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
read
Dummy module that prevents a signal from being removed during synthesis
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, (clk_sig, arstn_sig)
Flip-flop with asynchronous active-low reset
`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
deprecated Flip-flop with asynchronous active-low reset
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.
SystemVerilog Assertion Macros
The header file assertions.svh contains macros that expand to assertion blocks.
These macros should recduce the effort in writing many assertions and make it
easier to use them. They are identical with the macros used by lowrisc
and just re-implemented here for the sake of easier use in PULP projects (the same include guard is used so they should not clash).
Simple Assertion and Cover Macros
Macro
Arguments
Description
`ASSERT_I
__name, __prop
Immediate assertion
`ASSERT_INIT
__name, __prop
Assertion in initial block. Can be used for things like parameter checking
`ASSERT_FINAL
__name, __prop
Assertion in final block
`ASSERT
__name, __prop, (__clk, __rst)
Assert a concurrent property directly
`ASSERT_NEVER
__name, __prop, (__clk, __rst)
Assert a concurrent property NEVER happens
`ASSERT_KNOWN
__name, __sig, (__clk, __rst)
Concurrent clocked assertion with custom error message
`COVER
__name, __prop, (__clk, __rst)
Cover a concurrent property
The name of the clock and reset signals for implicit variants is clk_i and rst_ni, respectively.
Complex Assertion Macros
Macro
Arguments
Description
`ASSERT_PULSE
__name, __sig, (__clk, __rst)
Assert that signal is an active-high pulse with pulse length of 1 clock cycle
`ASSERT_IF
__name, __prop, __enable, (__clk, __rst)
Assert that a property is true only when an enable signal is set
`ASSERT_KNOWN_IF
__name, __sig, __enable, (__clk, __rst)
Assert that signal has a known value (each bit is either '0' or '1') after reset if enable is set
The name of the clock and reset signals for implicit variants is clk_i and rst_ni, respectively.
Assumption Macros
Macro
Arguments
Description
`ASSUME
__name, __prop, (__clk, __rst)
Assume a concurrent property
`ASSUME_I
__name, __prop
Assume an immediate property
The name of the clock and reset signals for implicit variants is clk_i and rst_ni, respectively.
Formal Verification Macros
Macro
Arguments
Description
`ASSUME_FPV
__name, __prop, (__clk, __rst)
Assume a concurrent property during formal verification only
`ASSUME_I_FPV
__name, __prop
Assume a concurrent property during formal verification only
`COVER_FPV
__name, __prop, (__clk, __rst)
Cover a concurrent property during formal verification
The name of the clock and reset signals for implicit variants is clk_i and rst_ni, respectively.
