CLaSH.Prelude.Mealy

Whereas the output of a Moore machine depends on the previous state, the outputof a Mealy machine depends on current transition.

Mealy machines are strictly more expressive, but may impose stricter timing requirements.

Mealy machine synchronised to the system clock

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

Mealy machine synchronised to an arbitrary clock

mealy'

Arguments

:: SClock clk

Clock to synchronize to

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

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

-> s

Initial state

-> Signal' clk i -> Signal' clk 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

type ClkA = Clk "A" 100

clkA :: SClock ClkA
clkA = sclock

topEntity :: Signal' ClkA (Int, Int) -> Signal' ClkA Int
topEntity = mealy' clkA 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' clkA100 Int, Signal' clkA100 Int)
        -> (Signal' clkA100 Int, Signal' clkA100 Int)
        -> Signal' clkA100 Int
dualMac (a,b) (x,y) = s1 + s2
  where
    s1 = mealy' clkA100 mac 0 (bundle' clkA100 (a,x))
    s2 = mealy' clkA100 mac 0 (bundle' clkA100 (b,y))

mealyB'

Arguments

:: (Bundle i, Bundle o)

=> SClock clk

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

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

-> s

Initial state

-> Unbundled' clk i -> Unbundled' clk 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 clk a b c = (b1,b2,i2)
  where
    (i1,b1) = unbundle' clk (mealy' clk f 0 (bundle' clk (a,b)))
    (i2,b2) = unbundle' clk (mealy' clk f 3 (bundle' clk (i1,c)))

Using mealyB' however we can write:

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