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How to crack ic 74ls154

How to crack ic 74ls154

Understanding the ic 74ls154

The 74LS154 is a 16-pin IC chip that contains a 16-line to 1-line decoder/demultiplexer. It takes a 4-bit binary input and activates one of the 16 output lines based on the input code. The 74LS154 is used in a variety of digital logic applications like address decoding, data routing, and Seven Segment Display driving.

To crack or hack the 74LS154, we need to understand its internal circuitry and logic first. Let’s take a look at the pin diagram and truth table of the 74LS154:


Methods to Crack the ic

There are a few methods that can be used to crack or hack the 74LS154:

1. Brute Force Attack

  • Try all possible 16 input combinations by applying voltages to the input pins and observe the output pins. This will help identify the input-output mapping.
  • Can be tedious but guarantees cracking of the IC.

2. De-capping and microscopic analysis

  • Carefully remove the plastic encapsulation of the IC chip.
  • Visually analyze the silicon die and trace the connections between transistors/gates.
  • Requires specialized equipment like microscopes, de-capping tools, etc.

3. Timing based analysis

  • Apply input signals with different timings and edge transitions.
  • Observe the propagation delays on output pins.
  • Determine logic relationships between inputs and outputs.
  • Needs high frequency pulse generator and oscilloscope.

Step-by-Step Process

Based on the above methods, the step-by-step process to crack the 74LS154 is:

1. Obtain the IC chip

  • Get a 74LS154 IC from old electronics or purchase a new one.

2. Connect power supplies

  • Connect +5V and GND pins to power the IC.

3. Connect input pins

  • Use switches or a microcontroller to generate logic states for input pins A, B, C, D.

4. Observe the outputs

  • Connect LEDs to the output pins to visually identify activated outputs.
  • Or use a logic analyzer to observe the 16 output pins.

5. Test all combinations

  • Vary the input pins across all 16 possibilities and note the corresponding output.
  • Map the input codes to output pins to determine the internal logic structure.

6. Repeat and validate

  • Repeat the process multiple times to check the consistency of input-output relationship.

Applications of Cracking 74LS154

Once the 74LS154 is cracked successfully, it can enable several applications:

  • Understanding the internal logic design and structure of the chip.
  • Modifying the behavior by altering input conditions.
  • Troubleshooting faulty ICs by comparing with expected behavior.
  • Designing compatible logic circuits using discrete components.
  • Learning the process of reverse engineering an IC.


Q1. What tools are required to crack the 74LS154 chip?

A1. Basic tools like breadboard, wires, 5V power supply, switches, LEDs, etc are required. Advanced tools like logic analyzer, oscilloscope, de-capping kit may help in faster cracking.

Q2. What precautions should be taken while cracking the IC?

A2. Handle the IC gently, avoid high current/voltages, use ESD protection. Decapping should be done carefully by skilled personnel.

Q3. What is the easiest method to crack the 74LS154?

A3. The brute force method of trying all input combinations is the easiest method to crack the 74LS154.

Q4. How long does it take to crack the IC using brute force?

A4. There are 16 possibilities so may take about 5-10 minutes on average to try all combinations manually.

Q5. Is cracking an IC illegal or unethical?

A5. Cracking ICs just for hobby, learning and academic purposes is usually considered legal and ethical. But malicious hacking may violate IP rights. Proceed responsibly.