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CLB.md

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Xilinx XC3000 CLB

A XC3000 CLB contains the following(from the Datasheet):

  • five logic variable inputs: A, B, C, D and E
  • a direct data in DI
  • an enable clock EC
  • a clock (invertible) K
  • an asynchronous direct RESET RD
  • two outputs X and Y

Pins

  • Inputs
    • A, B, C, D, E - Logic Variable Inputs
    • DI - Direct Data In
    • EC - Enable Clock
    • RD - Direct Reset (asynchronous)
    • K - Clock
  • Outputs
    • X and Y

Configuration

  • LCA Base

    • F - LUT5 mode, any function of 5 inputs:
      • F, G = func(A, [B, QX, QY], [C, QX, QY], D, E)
    • FG - 2x LUT4 mode, two functions of 4 inputs:
      • F = func(A, [B, QX, QY], [C, QX, QY], [D, E])
      • G = func(A, [B, QX, QY], [C, QX, QY], [D, E])
    • FGM - MUX between 2x LUT4:
      • func1 = func(A, [B, QX, QY], [C, QX, QY], D)
      • func2 = func(A, [B, QX, QY], [C, QX, QY], D)
      • F,G = E ? func2 : func1
  • X - select X function

    • F, QX - LUT output F or FlipFlop QX
  • Y - select Y function

    • G, QY - LUT output G or FlipFlop QY
  • DX - select data input for FlipFlop QX

    • DI, F, G - Direct Data In, LUT output F or LUT output G
  • DY - select data input for FlipFlop QY

    • DI, F, G - Direct Data In, LUT output F or LUT output G
  • CLK - clock config, only makes sense if X:QX or Y:QY

    • K, K:NOT - either positive or negative clock for whole CLB
  • RSTDIR - FlipFlop direct reset input used, only makes sense if X:QX or Y:QY

    • RD - use direct reset input
  • ENCLK - clock enable

    • EC - use clock enable
  • F - inputs for F function

    • A
    • B, QX or QY
    • C, QX or QY
    • D
    • E
  • G - inputs for G function

    • A
    • B, QX, or QY
    • C, QX, or QY
    • D
    • E