clash-prelude-1.8.1: Clash: a functional hardware description language - Prelude library
Copyright(C) 2015-2016 University of Twente
2019 Myrtle Software Ltd
2017 Google Inc.
2021-2022 QBayLogic B.V.
LicenseBSD2 (see the file LICENSE)
MaintainerQBayLogic B.V. <devops@qbaylogic.com>
Safe HaskellUnsafe
LanguageHaskell2010
Extensions
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Clash.Prelude.BlockRam.File

Description

Initializing a block RAM with a data file

Block RAM primitives that can be initialized with a data file. The BNF grammar for this data file is simple:

FILE = LINE+
LINE = BIT+
BIT  = '0'
     | '1'

Consecutive LINEs correspond to consecutive memory addresses starting at 0. For example, a data file memory.bin containing the 9-bit unsigned numbers 7 to 13 looks like:

000000111
000001000
000001001
000001010
000001011
000001100
000001101

Such a file can be produced with memFile:

writeFile "memory.bin" (memFile Nothing [7 :: Unsigned 9 .. 13])

We can instantiate a block RAM using the contents of the file above like so:

f :: (HiddenClock dom, HiddenEnable dom)
  => Signal dom (Unsigned 3)
  -> Signal dom (Unsigned 9)
f rd = unpack <$> blockRamFile d7 "memory.bin" rd (pure Nothing)

In the example above, we basically treat the block RAM as a synchronous ROM. We can see that it works as expected:

>>> import qualified Data.List as L
>>> L.tail $ sampleN 4 $ f (fromList [3..5])
[10,11,12]

However, we can also interpret the same data as a tuple of a 6-bit unsigned number, and a 3-bit signed number:

g :: (HiddenClock dom, HiddenEnable dom)
   => Signal dom (Unsigned 3)
   -> Signal dom (Unsigned 6,Signed 3)
g clk rd = unpack <$> blockRamFile d7 "memory.bin" rd (pure Nothing)

And then we would see:

>>> import qualified Data.List as L
>>> L.tail $ sampleN 4 $ g (fromList [3..5])
[(1,2),(1,3)(1,-4)]
Synopsis

Block RAM synchronized to an arbitrary clock

blockRamFile Source #

Arguments

:: (KnownNat m, Enum addr, NFDataX addr, HiddenClock dom, HiddenEnable dom, HasCallStack) 
=> SNat n

Size of the BRAM

-> FilePath

File describing the initial content of the BRAM

-> Signal dom addr

Read address r

-> Signal dom (Maybe (addr, BitVector m))

(write address w, value to write)

-> Signal dom (BitVector m)

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

Create a block RAM with space for n elements

  • NB: Read value is delayed by 1 cycle
  • NB: Initial output value is undefined, reading it will throw an XException
  • NB: This function might not work for specific combinations of code-generation backends and hardware targets. Please check the support table below:
VHDLVerilogSystemVerilog
Altera/QuartusBrokenWorksWorks
Xilinx/ISEWorksWorksWorks
ASICUntestedUntestedUntested

See also:

blockRamFilePow2 Source #

Arguments

:: forall dom n m. (KnownNat m, KnownNat n, HiddenClock dom, HiddenEnable dom, HasCallStack) 
=> FilePath

File describing the initial content of the BRAM

-> Signal dom (Unsigned n)

Read address r

-> Signal dom (Maybe (Unsigned n, BitVector m))

(write address w, value to write)

-> Signal dom (BitVector m)

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

Create a block RAM with space for 2^n elements

  • NB: Read value is delayed by 1 cycle
  • NB: Initial output value is undefined, reading it will throw an XException
  • NB: This function might not work for specific combinations of code-generation backends and hardware targets. Please check the support table below:
VHDLVerilogSystemVerilog
Altera/QuartusBrokenWorksWorks
Xilinx/ISEWorksWorksWorks
ASICUntestedUntestedUntested

See also:

Producing files

memFile Source #

Arguments

:: forall a f. (BitPack a, Foldable f, HasCallStack) 
=> Maybe Bit

Value to map don't care bits to. Nothing means throwing an error on don't care bits.

-> f a

Values to convert

-> String

Contents of the memory file

Convert data to the String contents of a memory file.

Example

The Maybe datatype has don't care bits, where the actual value does not matter. But the bits need a defined value in the memory. Either 0 or 1 can be used, and both are valid representations of the data.

>>> let es = [ Nothing, Just (7 :: Unsigned 8), Just 8]
>>> mapM_ (putStrLn . show . pack) es
0b0_...._....
0b1_0000_0111
0b1_0000_1000
>>> putStr (memFile (Just 0) es)
000000000
100000111
100001000
>>> putStr (memFile (Just 1) es)
011111111
100000111
100001000