Fixing Hardware Bug in 6551 York Chip for RS-232 Interface

Table of Contents:

1. Introduction
2. Setting Up the RS-232 Serial Interface
3. Configuring the 6551 Chip
4. Transmitting and Receiving Data
5. Working Around the Hardware Bug
6. Conclusion

🌟 Introduction

In this article, we will explore the functionality and setup of the 6551 York chip, which provides an RS-232 serial interface for the breadboard 6502 computer. We will discuss how this interface allows for the loading and running of more complex interactive programs on the computer.

🛠️ Setting Up the RS-232 Serial Interface

To utilize the 6551 York chip, we need to establish the necessary connections between the chip, the breadboard 6502 computer, and the data bus. We will modify the chip select and register select lines to make the four registers in the chip accessible at specific addresses. These four registers include the status register, control register, command register, and data register.

⚙️ Configuring the 6551 Chip

In this section, we will delve into the details of the four registers in the 6551 chip: the status register, control register, command register, and data register. We will focus on the significance of each register and the various status bits they provide. While we will not be using all the features initially, we will pay attention to the transmit and receive data register empty bits, which inform us about the status of data transmission and reception.

📡 Transmitting and Receiving Data

To transmit and receive data through the RS-232 interface, we need to understand the process involved. We will examine how to write to the data register to transmit data and how to read from the status register to check the transmit and receive data register empty bits. By monitoring these bits, we can ensure that data is transmitted and received correctly.

🐛 Working Around the Hardware Bug

Unfortunately, the 6551 York chip has a hardware bug that affects the transmit data register empty bit in the status register. This bug always reports the transmit buffer as empty, even when it is not. We will discuss the workaround for this bug, which involves adding a delay to the code after transmitting a character. This delay allows for the proper transmission of data without overwriting previously transmitted characters.

✅ Conclusion

In conclusion, the 6551 York chip provides an important RS-232 serial interface to the breadboard 6502 computer, enabling more complex interactive programs. By understanding the configuration and functionality of the chip, as well as working around the hardware bug, we can effectively transmit and receive data through the serial interface. Stay tuned for the next steps in utilizing this interface to run interactive programs on the computer.

Article:

🌟 Introduction

The 6551 York chip is a valuable addition to the breadboard 6502 computer, as it provides an RS-232 serial interface. This interface opens up possibilities for running more complex and interactive programs on the computer. In this article, we will explore the setup and configuration of the 6551 chip, as well as the process of transmitting and receiving data.

🛠️ Setting Up the RS-232 Serial Interface

Before we can start utilizing the capabilities of the 6551 chip, we need to establish the necessary connections. The chip should be connected to the data bus, and the chip select and register select lines should be hooked up to specific address lines and decode logic. This setup ensures that the four registers in the chip, namely the status register, control register, command register, and data register, are accessible at the desired addresses.

⚙️ Configuring the 6551 Chip

Now that the RS-232 serial interface is set up, it's time to dive into the configuration of the 6551 chip. Let's start by examining the status register, which provides valuable information about the status of the chip and ongoing data transmission. We'll particularly focus on the transmit data register empty and receive data register full bits, as they inform us about the availability of data for transmission and reception.

📡 Transmitting and Receiving Data

To effectively transmit and receive data through the RS-232 interface, we need to understand the process involved. When transmitting data, we write it to the data register, which then goes into the transmit data register. Monitoring the transmit data register empty bit in the status register helps us determine when the register is ready to receive the next byte. Similarly, the receive data register full bit in the status register informs us when data has been received and is ready to be read.

🐛 Working Around the Hardware Bug

Unfortunately, the 6551 York chip has a hardware bug that affects the transmit data register empty bit in the status register. This bug incorrectly reports the transmit buffer as empty even when it is not. To work around this issue, we can add a delay after transmitting each character to ensure that the transmission is complete before proceeding with the next byte. By implementing this delay, we can avoid overwriting previously transmitted characters and ensure the correct transmission of data.

✅ Conclusion

In conclusion, the 6551 York chip is a valuable asset for the breadboard 6502 computer, enabling the use of an RS-232 serial interface. By following the proper setup and configuration procedures, as well as working around the hardware bug, we can effectively transmit and receive data through the serial interface. This opens up exciting possibilities for running a wide range of interactive programs on the computer. Stay tuned for the next steps in exploring the full potential of the 6551 chip.

Highlights:

• The 6551 York chip provides an RS-232 serial interface to the breadboard 6502 computer.
• Setting up the chip requires connecting it to the data bus and configuring the chip select and register select lines.
• The four registers in the 6551 chip are the status register, control register, command register, and data register.
• The transmit and receive data register empty bits in the status register play a crucial role in data transmission and reception.
• The 6551 chip has a hardware bug that affects the transmit data register empty bit, requiring a workaround with a delay.
• With the proper setup and configuration, the serial interface enables more complex and interactive programs on the computer.

FAQ:

Q: What is the purpose of the 6551 York chip? A: The 6551 chip provides an RS-232 serial interface to the breadboard 6502 computer, enabling the transmission and reception of data.

Q: What are the four registers in the 6551 chip? A: The four registers are the status register, control register, command register, and data register. They play a crucial role in configuring and managing the chip's functionality.

Q: How does the hardware bug in the 6551 chip affect data transmission? A: The hardware bug causes the transmit data register empty bit in the status register to always report as empty, even when it is not. This can lead to overwritten data if not addressed properly.

Q: What is the workaround for the hardware bug? A: The workaround involves adding a delay after transmitting each character to ensure the completion of the transmission before moving on to the next byte.

Q: How can the serial interface be used to run interactive programs? A: The serial interface allows for the transmission and reception of data, enabling the exchange of information between the breadboard 6502 computer and external devices. This capability opens up possibilities for running more complex and interactive programs on the computer.