Adds linear feedback shift register component #108
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| // Copyright (C) 2023 Intel Corporation | |||
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remove blank (uncommented) lines in the header?
| /// The name of the signal (and output pin) for the [i]th stage. | ||
| String _stageName(int i) => '${dataName}_stage_$i'; | ||
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| LinearFeedbackShiftRegister(Logic dataIn, |
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add a doc comment to the constructor
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| if (reset != null) { | ||
| reset = addInput('reset', reset); | ||
| if (resetValue != null) { |
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the original shift register was recently upgraded to allow for a List resetValue to control each element of the register (https://github.com/intel/rohd-hcl/blob/main/lib/src/shift_register.dart). However, since the LFSR is always 1-wide, maybe a different API makes sense. The current resetValue just allows you to basically set all flops to 0 or 1. Should we allow a bitvector of width == shifts to initialize the LFSR?
| Logic lsb = state.getRange(0, 1); // Get LSB (least significant bit) | ||
| state = [Const(0, width: 1), state.getRange(1, width)].swizzle(); | ||
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| If(lsb.eq(Const(1)), then: [ |
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This If (capitalized) creates a Conditional object which only executes under certain conditions (e.g. within a Sequential or Combinational), but the object is not included in one, so it will never take effect.
| state = [Const(0, width: 1), state.getRange(1, width)].swizzle(); | ||
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| If(lsb.eq(Const(1)), then: [ | ||
| state < state ^ taps // Perform XOR and assign back to state |
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If taps is a Logic, then it should be created as an input to the module. I'm not sure it's necessary to support dynamic re-muxing of the LFSR, in which case the taps could be a non-Logic (e.g. a List<bool>, or maybe some int/BigInt where the bits correspond to the polynomial
| {required Logic clk, | ||
| required this.state, | ||
| required this.shifts, | ||
| required this.taps, |
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Careful using this. for inputs of a module, since we want to replace them using addInput
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| await lfsr.build(); | ||
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| final expectedData = [8, 12, 6, 3, 9, 4, 2, 1]; |
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how did you determine the expected values?
Description & Motivation
Added a Galois linear feedback shift register component.
Related Issue(s)
N/A
Testing
Added unit tests for new component. Ran unit tests individually and using dart test.
Backwards-compatibility
No.
Documentation
Will need to add page for LFSR implementation