Module Hardcaml.Bits

the empty signal

names a signal

let a = a -- "a" in ...

signals may have multiple names.

returns the width (number of bits) of a signal.

let w = width s in ...

addess_bits_for num_elements returns the address width required to index num_elements.

It is the same as Int.ceil_log2, except it wll return a minimum value of 1 (since you cannot have 0 width vectors). Raises if num_elements is < 0.

num_bits_to_represent x returns the number of bits required to represent the number x, which should be >= 0.

convert binary string to constant

convert integer to constant

convert unsigned hex string to constant

convert signed hex string to constant

convert decimal string to constant

convert verilog style string to constant

convert IntbitsList to constant

convert verilog style or binary string to constant

concat ts concatenates a list of signals - the msb of the head of the list will become the msb of the result.

let c = concat [ a; b; c ] in ...

concat raises if ts is empty or if any t in ts is empty.

same as concat except empty signals are first filtered out

concatenate two signals.

let c = a @: b in ...

equivalent to concat [ a; b ]

logic 1

logic 0

zero w makes a the zero valued constant of width w

ones w makes a constant of all ones of width w

one w makes a one valued constant of width w

select t hi lo selects from t bits in the range hi...lo, inclusive. select raises unless hi and lo fall within 0 .. width t - 1 and hi >= lo.

same as select except invalid indices return empty

select a single bit

get most significant bit

get least significant bits

get least significant bit

get most significant bits

drop_bottom s n drop bottom n bits of s

drop_top s n drop top n bits of s

sel_bottom s n select bottom n bits of s

sel_top s n select top n bits of s

insert ~into:t x ~at_offset insert x into t at given offet

multiplexer.

let m = mux sel inputs in ...

Given l = List.length inputs and w = width sel the following conditions must hold.

l <= 2**w, l >= 2

If l < 2**w, the last input is repeated.

All inputs provided must have the same width, which will in turn be equal to the width of m.

mux2 c t f 2 input multiplexer. Selects t if c is high otherwise f.

t and f must have same width and c must be 1 bit.

Equivalent to mux c [f; t]

case mux

match mux

logical and

a <>:. 0 &: b <>:. 0

logical or

a <>:. 0 |: b <>:. 0

logic xor

logical not

addition

subtraction

negation

unsigned multiplication

signed multiplication

equality

inequality

less than

greater than

less than or equal to

greater than or equal to

signed less than

signed greater than

signed less than or equal to

signed greated than or equal to

create string from signal

to_int t treats t as unsigned and resizes it to fit exactly within an OCaml Int.t.

• If width t > Int.num_bits then the upper bits are truncated.
• If width t >= Int.num_bits and bit t (Int.num_bits-1) = vdd (i.e. the msb of the resulting Int.t is set), then the result is negative.
• If t is Signal.t and not a constant value, an exception is raised.

to_sint t treats t as signed and resizes it to fit exactly within an OCaml Int.t.

• If width t > Int.num_bits then the upper bits are truncated.
• If t is Signal.t and not a constant value, an exception is raised.

create binary string from signal

convert signal to a list of bits, msb first

to_array s convert signal s to array of bits with lsb at index 0

of_array a convert array a of bits to signal with lsb at index 0

repeat signal n times

split signal in half

Split signal into a list of signals with width equal to part_width. The least significant bits are at the head of the returned list. If exact is true the input signal width must be exactly divisable by part_width.

shift left logical

shift right logical

shift right arithmetic

shift by variable amount

uresize t w returns the unsigned resize of t to width w. If w = width t, this is a no-op. If w < width t, this selects the w low bits of t. If w > width t, this extends t with zero (width t - w).

sresize t w returns the signed resize of t to width w. If w = width t, this is a no-op. If w < width t, this selects the w low bits of t. If w > width t, this extends t with width t - w copies of msb t.

unsigned resize by +1 bit

signed resize by +1 bit

resize_list ?resize l finds the maximum width in l and applies resize el max to each element.

resize_op2 ~resize f a b applies resize x w to a and b where w is the maximum of their widths. It then returns f a b

fold 'op' though list

reverse bits

mod_counter max t is if t = max then 0 else (t + 1), and can be used to count from 0 to (max-1) then from zero again. If max == 1<<n, then a comparator is not generated and overflow arithmetic used instead. If

tree ~arity ~f input creates a tree of operations. The arity of the operator is configurable. tree raises if input = [].

priority_select cases returns the value associated with the first case whose valid signal is high. valid will be set low in the returned With_valid.t if no case is selected.

Same as priority_select except returns default if no case matches.

Select a case where one and only one valid signal is enabled. If more than one case is valid then the return value is undefined. If no cases are valid, 0 is returned by the current implementation, though this should not be relied upon.

popcount t returns the number of bits set in t.

is_pow2 t returns a bit to indicate if t is a power of 2.

leading_ones t returns the number of consecutive 1s from the most significant bit of t down.

trailing_ones t returns the number of consecutive 1s from the least significant bit of t up.

leading_zeros t returns the number of consecutive 0s from the most significant bit of t down.

trailing_zeros t returns the number of consecutive 0s from the least significant bit of t up.

floor_log2 x returns the floor of log-base-2 of x. x is treated as unsigned and an error is indicated by valid = gnd in the return value if x = 0.

ceil_log2 x returns the ceiling of log-base-2 of x. x is treated as unsigned and an error is indicated by valid = gnd in the return value if x = 0.

convert binary to onehot

convert onehot to binary

convert binary to gray code

convert gray code to binary

create random constant vector of given width

Unsigned operations compatible with type t

Signed operations compatible with type t