RAM module testing and troubleshooting

Summary

In this video, the creator tests a self-built RAM module by powering it up and verifying its functionality. They check for correct data storage and retrieval, addressing issues with wiring and pull-up resistors. The video demonstrates writing zeros and ones to memory, reading data back, and using control signals for input and output. The creator also troubleshoots a wiring mistake, discusses the importance of edge detection for RAM writing, and labels control signals for clarity. The video concludes with a functional RAM module and plans for future videos on the program counter and a binary to decimal converter.

Takeaways

• 😀 The video is focused on testing a RAM module to ensure it's functioning correctly.
• 🔌 The initial power-up of the RAM module revealed the clock was running, and the module was in program mode.
• 💡 The video demonstrates writing zeros to memory, which unexpectedly resulted in ones, indicating a potential default input issue.
• 🔍 Upon inspection, it was discovered that some wires were connected incorrectly, specifically power and ground connections were off by one pin.
• 🛠️ The video shows a hands-on approach to fixing the wiring issue, which was crucial for the proper operation of the RAM module.
• 📈 After fixing the wiring, the RAM module was tested again, and it was observed that writing different patterns to memory worked as expected.
• 🔄 The video explains the process of reading data from memory and outputting it to the bus, showcasing the functionality of the memory address register.
• 🔧 The script includes a troubleshooting session where the presenter identifies and corrects an issue with the RAM in signal and its interaction with the clock signal.
• 💻 The video concludes with the addition of labels to various control signals for convenience and better understanding of the system.
• 📚 The presenter plans to work on the program counter and the output register in upcoming videos, with the latter involving a binary to decimal converter.

Q & A

What was the initial problem the presenter encountered when testing the RAM module?

The initial problem was that the RAM module was writing all ones instead of zeros, which suggested a potential issue with the wiring or connections.

Why did the presenter suspect that the default input might be '1'?

The presenter suspected the default input might be '1' because the inputs on the 7400 series and 74 LS series chips are pulled up with pull-up resistors, which would result in a '1' if nothing is connected.

What was the wiring mistake that the presenter identified during the testing?

The wiring mistake was that the power should have been going to pin 16, but it was connected to pin 15, and the ground should have been going to pin 15 but was connected to pin 14.

How did the presenter confirm that the wiring issue was fixed?

The presenter confirmed the wiring issue was fixed by writing zeros to the memory and observing that the memory now correctly reflected the written zeros.

What is the purpose of the memory address register in the RAM module?

The memory address register is used to select a specific memory location to read from or write to within the RAM module.

Why did the presenter decide to label the control signals?

The presenter decided to label the control signals to make it easier to understand and manage the various signals during testing and future reference.

What is the function of the RAM in signal as described in the script?

The RAM in signal is used to write data from the bus into the RAM memory. It is active high and is used to transfer data during the leading edge of the clock signal.

How did the presenter create an edge detector circuit to control the RAM in signal?

The presenter created an edge detector circuit by using a 0.01 microfarad capacitor and a 1k ohm resistor, which charges during the high state of the clock signal and discharges quickly, creating a short high pulse that triggers the RAM in signal.

What is the significance of the 10 microseconds delay in the edge detector circuit?

The 10 microseconds delay ensures that the RAM in signal is only high for the leading edge of the clock pulse, allowing data to be written to the RAM during just that moment.

What is the next step the presenter plans to take after testing the RAM module?

The next steps the presenter plans to take are to work on the program counter circuit and then proceed to the output register, which will involve creating a binary to decimal converter.