Clash.Prelude.BlockRam.File

Initialising a BlockRAM with a data file

BlockRAM primitives that can be initialised 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 number 7 to 13 looks like:

000000111
000001000
000001001
000001010
000001011
000001100
000001101

We can instantiate a BlockRAM using the content of the above file like so:

f :: HiddenClock domain -> Signal domain (Unsigned 3) -> Signal domain (Unsigned 9)
f rd = unpack <$> exposeClock blockRamFile clk d7 "memory.bin" rd (signal Nothing)

In the example above, we basically treat the BlockRAM as an 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 domain -> Signal domain (Unsigned 3) -> Signal domain (Unsigned 6,Signed 3)
g clk rd = unpack <$> exposeClock blockRamFile clk d7 "memory.bin" rd (signal 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)]

BlockRAM synchronised to an arbitrary clock

blockRamFile

Arguments

:: (KnownNat m, Enum addr, HiddenClock domain gated, HasCallStack)

=> SNat n

Size of the blockRAM

-> FilePath

File describing the initial content of the blockRAM

-> Signal domain addr

Read address r

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

(write address w, value to write)

-> Signal domain (BitVector m)

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

• NB: This function might not work for specific combinations of code-generation backends and hardware targets. Please check the support table below:

                 | VHDL     | Verilog  | SystemVerilog |
  ===============+==========+==========+===============+
  Altera/Quartus | Broken   | Works    | Works         |
  Xilinx/ISE     | Works    | Works    | Works         |
  ASIC           | Untested | Untested | Untested      |
  ===============+==========+==========+===============+
  

Additional helpful information:

• See Clash.Prelude.BlockRam for more information on how to use a Block RAM.
• Use the adapter readNew' for obtaining write-before-read semantics like this: readNew' clk (blockRamFile' clk size file) rd wrM.
• See Clash.Prelude.BlockRam.File for more information on how to instantiate a Block RAM with the contents of a data file.
• See Clash.Sized.Fixed for ideas on how to create your own data files.

blockRamFilePow2

Arguments

:: (KnownNat m, KnownNat n, HiddenClock domain gated, HasCallStack)

=> FilePath

File describing the initial content of the blockRAM

-> Signal domain (Unsigned n)

Read address r

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

(write address w, value to write)

-> Signal domain (BitVector m)

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

• NB: This function might not work for specific combinations of code-generation backends and hardware targets. Please check the support table below:

                 | VHDL     | Verilog  | SystemVerilog |
  ===============+==========+==========+===============+
  Altera/Quartus | Broken   | Works    | Works         |
  Xilinx/ISE     | Works    | Works    | Works         |
  ASIC           | Untested | Untested | Untested      |
  ===============+==========+==========+===============+
  

Additional helpful information:

• See Clash.Prelude.BlockRam for more information on how to use a Block RAM.
• Use the adapter readNew' for obtaining write-before-read semantics like this: readNew' clk (blockRamFilePow2' clk file) rd wrM.
• See Clash.Prelude.BlockRam.File for more information on how to instantiate a Block RAM with the contents of a data file.
• See Clash.Sized.Fixed for ideas on how to create your own data files.