CLaSH.Prelude

CλaSH (pronounced ‘clash’) is a functional hardware description language that borrows both its syntax and semantics from the functional programming language Haskell. The merits of using a functional language to describe hardware comes from the fact that combinational circuits can be directly modeled as mathematical functions and that functional languages lend themselves very well at describing and (de-)composing mathematical functions.

This package provides:

• Prelude library containing datatypes and functions for circuit design

To use the library:

• Import CLaSH.Prelude
• Additionally import CLaSH.Prelude.Explicit if you want to design explicitly clocked circuits in a multi-clock setting

For now, CLaSH.Prelude is also the best starting point for exploring the library. A preliminary version of a tutorial can be found in CLaSH.Tutorial.

Creating synchronous sequential circuits

mealy

Arguments

:: (s -> i -> (s, o))

Transfer function in mealy machine form: state -> input -> (newstate,output)

-> s

Initial state

-> Signal i -> Signal o

Synchronous sequential function with input and output matching that of the mealy machine

Create a synchronous function from a combinational function describing a mealy machine

mac :: Int        -- Current state
    -> (Int,Int)  -- Input
    -> (Int,Int)  -- (Updated state, output)
mac s (x,y) = (s',s)
  where
    s' = x * y + s

topEntity :: Signal (Int, Int) -> Signal Int
topEntity = mealy mac 0

>>> simulate topEntity [(1,1),(2,2),(3,3),(4,4)]
[0,1,5,14...

Synchronous sequential functions can be composed just like their combinational counterpart:

dualMac :: (Signal Int, Signal Int)
        -> (Signal Int, Signal Int)
        -> Signal Int
dualMac (a,b) (x,y) = s1 + s2
  where
    s1 = mealy mac 0 (bundle (a,x))
    s2 = mealy mac 0 (bundle (b,y))

mealyB

Arguments

:: (Bundle i, Bundle o)

=> (s -> i -> (s, o))

Transfer function in mealy machine form: state -> input -> (newstate,output)

-> s

Initial state

-> Unbundled i -> Unbundled o

Synchronous sequential function with input and output matching that of the mealy machine

A version of mealy that does automatic Bundleing

Given a function f of type:

f :: Int -> (Bool, Int) -> (Int, (Int, Bool))

When we want to make compositions of f in g using mealy, we have to write:

g a b c = (b1,b2,i2)
  where
    (i1,b1) = unbundle (mealy f 0 (bundle (a,b)))
    (i2,b2) = unbundle (mealy f 3 (bundle (i1,c)))

Using mealyB however we can write:

g a b c = (b1,b2,i2)
  where
    (i1,b1) = mealyB f 0 (a,b)
    (i2,b2) = mealyB f 3 (i1,c)

(<^>)

Arguments

:: (Bundle i, Bundle o)

=> (s -> i -> (s, o))

Transfer function in mealy machine form: state -> input -> (newstate,output)

-> s

Initial state

-> Unbundled i -> Unbundled o

Synchronous sequential function with input and output matching that of the mealy machine

Infix version of mealyB

registerB :: Bundle a => a -> Unbundled a -> Unbundled a

Create a register function for product-type like signals (e.g. '(Signal a, Signal b)')

rP :: (Signal Int,Signal Int) -> (Signal Int, Signal Int)
rP = registerB (8,8)

>>> simulateB rP [(1,1),(2,2),(3,3)] :: [(Int,Int)]
[(8,8),(1,1),(2,2),(3,3)...

BlockRAM primitives

blockRam

Arguments

:: (KnownNat n, KnownNat m)

=> Vec n a

Initial content of the BRAM, also determines the size, n, of the BRAM.

NB: MUST be a constant.

-> Signal (Unsigned m)

Write address w

-> Signal (Unsigned m)

Read address r

-> Signal Bool

Write enable

-> Signal a

Value to write (at address w)

-> Signal a

Value of the blockRAM at address r from the previous clock cycle

Create a blockRAM with space for n elements.

• NB: Read value is delayed by 1 cycle
• NB: Initial output value is undefined

bram40 :: Signal (Unsigned 6) -> Signal (Unsigned 6) -> Signal Bool
       -> Signal Bit -> Signal Bit
bram40 = blockRam (replicate d40 1)

blockRamPow2

Arguments

:: (KnownNat (2 ^ n), KnownNat n)

=> Vec (2 ^ n) a

Initial content of the BRAM, also determines the size, 2^n, of the BRAM.

NB: MUST be a constant.

-> Signal (Unsigned n)

Write address w

-> Signal (Unsigned n)

Read address r

-> Signal Bool

Write enable

-> Signal a

Value to write (at address w)

-> Signal a

Value of the blockRAM at address r from the previous clock cycle

Create a blockRAM with space for 2^n elements

• NB: Read value is delayed by 1 cycle
• NB: Initial output value is undefined

bram32 :: Signal (Unsigned 5) -> Signal (Unsigned 5) -> Signal Bool
       -> Signal Bit -> Signal Bit
bram32 = blockRamPow2 (replicate d32 1)

Utility functions

window

Arguments

:: (KnownNat n, Default a)

=> Signal a

Signal to create a window over

-> Vec (n + 1) (Signal a)

Window of at least size 1

Give a window over a Signal

window4 :: Signal Int -> Vec 4 (Signal Int)
window4 = window

>>> simulateB window4 [1::Int,2,3,4,5] :: [Vec 4 Int]
[<1,0,0,0>,<2,1,0,0>,<3,2,1,0>,<4,3,2,1>,<5,4,3,2>...

windowD

Arguments

:: (KnownNat (n + 1), Default a)

=> Signal a

Signal to create a window over

-> Vec (n + 1) (Signal a)

Window of at least size 1

Give a delayed window over a Signal

windowD3 :: Signal Int -> Vec 3 (Signal Int)
windowD3 = windowD

>>> simulateB windowD3 [1::Int,2,3,4] :: [Vec 3 Int]
[<0,0,0>,<1,0,0>,<2,1,0>,<3,2,1>,<4,3,2>...

isRising

Arguments

:: (Bounded a, Eq a)

=> a

Starting value

-> Signal a

-> Signal Bool

Give a pulse when the Signal goes from minBound to maxBound

isFalling

Arguments

:: (Bounded a, Eq a)

=> a

Starting value

-> Signal a

-> Signal Bool

Give a pulse when the Signal goes from maxBound to minBound

Testbench functions

assert

Arguments

:: (Eq a, Show a)

=> Signal' t a

Checked value

-> Signal' t a

Expected value

-> Signal' t b

Return valued

-> Signal' t b

Compares the first two arguments for equality and logs a warning when they are not equal. The second argument is considered the expected value. This function simply returns the third argument unaltered as its result. This function is used by coutputVerifier.

NB: This function is can be used in synthesizable designs.

stimuliGenerator

Arguments

:: KnownNat l

=> Vec l a

Samples to generate

-> Signal a

Signal of given samples

To be used as a one of the functions to create the "magical" testInput value, which the CλaSH compilers looks for to create the stimulus generator for the generated VHDL testbench.

Example:

testInput :: Signal Int
testInput = stimuliGenerator $(v [(1::Int),3..21])

>>> sampleN 13 testInput
[1,3,5,7,9,11,13,15,17,19,21,21,21]

outputVerifier

Arguments

:: (KnownNat l, Eq a, Show a)

=> Vec l a

Samples to compare with

-> Signal a

Signal to verify

-> Signal Bool

Indicator that all samples are verified

To be used as a functions to generate the "magical" expectedOutput function, which the CλaSH compilers looks for to create the signal verifier for the generated VHDL testbench.

Example:

expectedOutput :: Signal Int -> Signal Bool
expectedOutput = outputVerifier $(v ([70,99,2,3,4,5,7,8,9,10]::[Int]))

>>> import qualified Data.List as List
>>> sampleN 12 (expectedOutput (fromList ([0..10] List.++ [10,10,10])))
[
expected value: 70, not equal to actual value: 0
False,
expected value: 99, not equal to actual value: 1
False,False,False,False,False,
expected value: 7, not equal to actual value: 6
False,
expected value: 8, not equal to actual value: 7
False,
expected value: 9, not equal to actual value: 8
False,
expected value: 10, not equal to actual value: 9
False,True,True]

Exported modules

Synchronous signals

module CLaSH.Signal

module CLaSH.Signal.Delayed

DataFlow interface

module CLaSH.Prelude.DataFlow

Datatypes

Bit vectors

module CLaSH.Sized.BitVector

module CLaSH.Prelude.BitIndex

module CLaSH.Prelude.BitReduction

Arbitrary-width numbers

module CLaSH.Sized.Signed

module CLaSH.Sized.Unsigned

module CLaSH.Sized.Index

Fixed point numbers

module CLaSH.Sized.Fixed

Fixed size vectors

module CLaSH.Sized.Vector

Type-level natural numbers

module GHC.TypeLits

module CLaSH.Promoted.Nat

module CLaSH.Promoted.Nat.Literals

module CLaSH.Promoted.Nat.TH

Type-level functions

module CLaSH.Promoted.Ord

Template Haskell

class Lift t where

Methods

lift :: t -> Q Exp

Instances

Lift Bool

Lift Char

Lift Double

Lift Float

Lift Int

Lift Int8

Lift Int16

Lift Int32

Lift Int64

Lift Integer

Lift Word

Lift Word8

Lift Word16

Lift Word32

Lift Word64

Lift ()

Lift Natural

Lift a => Lift [a]

Integral a => Lift (Ratio a)

Lift a => Lift (Maybe a)

KnownNat n => Lift (Index n)

KnownNat n => Lift (BitVector n)

KnownNat n => Lift (Signed n)

KnownNat n => Lift (Unsigned n)

(Lift a, Lift b) => Lift (Either a b)

(Lift a, Lift b) => Lift (a, b)

Lift a => Lift (Signal' clk a)

Lift a => Lift (Vec n a)

Lift a => Lift (DSignal delay a)

(Lift a, Lift b, Lift c) => Lift (a, b, c)

(Lift (rep ((+) int frac)), KnownNat frac, KnownNat int, Typeable (Nat -> *) rep) => Lift (Fixed rep int frac)

(Lift a, Lift b, Lift c, Lift d) => Lift (a, b, c, d)

(Lift a, Lift b, Lift c, Lift d, Lift e) => Lift (a, b, c, d, e)

(Lift a, Lift b, Lift c, Lift d, Lift e, Lift f) => Lift (a, b, c, d, e, f)

(Lift a, Lift b, Lift c, Lift d, Lift e, Lift f, Lift g) => Lift (a, b, c, d, e, f, g)

deriveLift :: Name -> Q [Dec]

Derive Lift instances for the given datatype.

Type classes

CLaSH

module CLaSH.Class.BitPack

module CLaSH.Class.Num

module CLaSH.Class.Resize

Other

module Control.Applicative

module Data.Bits

module Data.Default

Haskell Prelude

CLaSH.Prelude re-exports most of the Haskell Prelude with the exception of the following: (++), (!!), concat, drop, foldl, foldl1, foldr, foldr1, head, init, iterate, last, length, map, repeat, replicate, reverse, scanl, scanr, splitAt, tail, take, unzip, unzip3, zip, zip3, zipWith, zipWith3.

It instead exports the identically named functions defined in terms of Vec at CLaSH.Sized.Vector.

module Prelude