RAM module build - part 2

Summary

In this instructional video, the presenter builds a 16-byte memory system with 4 address lines and 8 data lines, utilizing a 74 LS173 4-bit register for address selection. They explain how to connect the address lines to the register and introduce a programming mode using DIP switches for manual address and data setting. A 74 LS157 quad two-line to one-line data selector is employed to toggle between the DIP switches and the address register. The video concludes with a demonstration of switching between run and program modes, setting up for future data line configuration.

Takeaways

• 😀 The video discusses building a 16-byte memory system with four address lines and eight data lines.
• 🛠️ A 74 LS 173 4-bit register is used to connect the memory address lines to the address register.
• 🕹️ The memory system includes an 8-bit Tri-State buffer for outputting data to a bus.
• 🔌 The clock module is connected to the memory system, even though it's not directly related, for layout purposes.
• 🔄 The 74 LS 157 quad two-line to one-line data selector is introduced to toggle between the address register and dip switches.
• 🔲 The video demonstrates how to use dip switches to manually set memory addresses for programming the computer.
• 🔵🔴 Indicator LEDs are used to show the current mode of operation (programming or run mode).
• 🔑 A double throw switch is used to toggle between programming mode (using dip switches) and run mode (using the address register).
• 🔄 The video shows how to connect the address register outputs to the memory address inputs and verify the functionality.
• 🔍 The process of switching between different memory addresses using the address register or dip switches is demonstrated.

Q & A

What is the purpose of the 16-byte memory being built in the video?

The purpose of the 16-byte memory is to store 16 bytes of data, which can be read from or written to using the four address lines, eight data lines, and an 8-bit Tri-State buffer for output to a bus.

What is the function of the 74 LS 173 in the memory system described?

The 74 LS 173 is used as a 4-bit register to store the memory address, allowing the system to select which of the 16 bytes is being read or written to.

Why is the clock module connected to the memory system even though it's not directly related?

The clock module is connected to the memory system for layout purposes, as the final computer design will have the clock module positioned just above the RAM.

How does the video demonstrate switching between programming mode and run mode?

The video demonstrates switching between programming mode and run mode by using a double throw switch to toggle between the dip switches and the address register, with indicator LEDs showing the current mode.

What is the role of the 74 LS 157 in the memory system?

The 74 LS 157 is used as a quad two-line to one-line data selector, allowing the system to choose between the address provided by the dip switches (programming mode) or the address from the address register (run mode).

How are the dip switches used in the memory system?

The dip switches are used to manually set the memory address in programming mode, allowing for direct input of data into specific memory locations.

What is the significance of the strobe input on the 74 LS 157 chip?

The strobe input on the 74 LS 157 chip acts as a master enable. When the strobe is low, it enables the chip, allowing the selection between the A and B inputs.

How does the memory system handle inputting data into the memory address register?

The memory system handles inputting data into the memory address register by using the data enable pins on the 74 LS 173 register, which control whether the input from the bus is clocked in on the clock pulse.

What is the purpose of the current limiting resistors used with the indicator LEDs?

The current limiting resistors are used with the indicator LEDs to prevent excessive current flow, which could burn out the LEDs, by limiting the current when they are connected directly to 5 volts.

How does the video ensure the memory system is not constantly resetting?

The video ensures the memory system is not constantly resetting by managing the clear signal on the 74 LS 173 register, which needs to be kept low to prevent constant clearing of the register.