Coding & Line Codes

8-Bit Parallel Descrambler

Combinational 8-bit parallel descrambler using a fixed XOR mask to reverse scrambling operations.

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About this block

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8-Bit Parallel Descrambler is a Verilog reference block in the Coding & Line Codes catalog. Line codes, serializers, and digital encoding/decoding blocks. Marked Easy: a small block you can read, simulate, and synthesize in one sitting.

This IP implements a combinational 8-bit parallel descrambler. It reverses a fixed XOR scrambling operation using a predefined mask. The design is purely combinational with no internal state or clock dependency.

The module applies a bitwise XOR operation between the input data and a constant mask. The mask value is defined as 8'hB7 in the RTL. This operation is symmetric, meaning applying the same mask again restores the original data.

This IP provides a simple, efficient method for reversing a fixed XOR scramble. It is suitable for applications requiring lightweight data obfuscation reversal. The design is synthesizable and has been verified via Icarus Verilog.

Choose Open in IDE. RTL Studio loads the packaged workspace for 8-Bit Parallel Descrambler.
Read the Verilog module in the editor. The catalog line for this block: Combinational 8-bit parallel descrambler using a fixed XOR mask to reverse scrambling operations.
Run the packaged testbench with the in-browser Verilator simulator, then open the VCD in the waveform viewer.
Run Yosys in the same IDE for a generic netlist. Sky130 liberty mapping is a separate Pro library option.

RTL Studio is the Verilog simulator and IDE around this block: Slang lint, Verilator, VCD waveforms, and Yosys, in the browser. Simulation guide · Yosys guide.

Ports

Port Name	Direction	Width	Description
data_in	Input	[7:0]	8-bit data input to be descrambled
data_out	Output	[7:0]	8-bit data output after descrambling

Architecture

The following diagram illustrates the data flow within the module.

The core logic is a single assignment statement: assign data_out = data_in ^ 8'hB7;

Verification

The testbench verifies the functionality against expected XOR results. All test cases passed successfully during simulation.

Test Case	Input Hex	Expected Output	Actual Output	Status
TC1	0x00	0xB7	0xB7	PASS
TC2	0xFF	0x48	0x48	PASS
TC3	0x5A	0xED	0xED	PASS
TC4	0xA5	0x12	0x12	PASS
TC5	0x3C	0x8B	0x8B	PASS
TC6	0x00-0x28	data_in ^ 0xB7	Correct	PASS

Simulation logs confirm zero errors across all manual and loop-based tests. Use the RtlStudio Waveform tab with sim/dump.vcd to inspect signal transitions.

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