Learn to Fix Hardware Bug in 6551 York Chip for Reliable Serial Communication

Table of Contents:

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

Introduction

In this article, we will explore the 6551 York chip, which provides an RS-232 serial interface to a breadboard 6502 computer. This serial interface allows us to load and run more complex interactive programs on the computer. We will walk through the process of setting up the interface, initializing the 6551 chip, receiving and sending data, and working around a hardware bug that affects the chip's functionality.

Setting Up the RS-232 Serial Interface

To begin, we need to establish the connection between the 6551 chip and the data bus of the breadboard 6502 computer. This involves connecting the eight data lines and the chip select and register select lines to the appropriate address lines and decode logic. By doing this, we can access the four registers of the chip at specific addresses. These registers include the status register, control register, command register, and data register.

Initializing the 6551 Chip

Once the RS-232 serial interface is set up, we can proceed with initializing the 6551 chip. This involves configuring the baud rate, stop bits, WORD length, and other settings using the control register. We will also take a closer look at the status register, which provides information about the transmitter and receiver data registers. By understanding the status bits, we can determine the status of sending and receiving data.

Receiving Data

To receive data, we need to continuously monitor the status of the receive data register full bit in the status register. When this bit is set, it means that an external device connected to the serial port has sent us data. We will use a loop to check if the receive data register is full, and if it is, we will read the data from the register and process it accordingly.

Sending Data

Sending data is similar to receiving data. We can use a subroutine to set the character we want to send in the data register. However, before sending each character, we need to check the transmit data register empty bit in the status register. We will use a loop to wait until the register becomes empty before sending the next character. This ensures that the characters are transmitted correctly and prevents data corruption.

Working Around the Hardware Bug

The 6551 chip has a known hardware bug that affects the transmit data register empty bit in the status register. The bit always reports as empty, even if the register is still transmitting data. To work around this bug, we can add a delay after sending each character to ensure that the transmit register is fully emptied. By calculating the required delay based on the baud rate, we can ensure reliable serial communication.

Conclusion

In conclusion, the 6551 York chip provides an RS-232 serial interface to the breadboard 6502 computer, allowing for more complex interactive programs. By setting up the serial interface, initializing the 6551 chip, and implementing methods to receive and send data, we can harness the power of serial communication. Despite the hardware bug, we can work around it and achieve reliable transmission and reception of data. Stay tuned for more exciting developments in running interactive programs on the breadboard 6502 computer.

⭐️ Highlights:

• Introduction to the 6551 York chip and its role in providing an RS-232 serial interface
• Step-by-step guide on setting up the chip and establishing the serial interface
• Description of the initialization process, including configuring baud rate, stop bits, and word length
• Explanation of how to receive data using the receive data register and status register
• Overview of the procedure for sending data, including checking the transmit data register empty bit
• Workaround for the hardware bug affecting the transmit data register empty bit
• Conclusion highlighting the benefits of using the 6551 chip for serial communication

🌐 Resources:

• eater.net 6502 (website for 6502 breadboard computer kits)

FAQ:

Q: What is the purpose of the 6551 York chip? A: The 6551 York chip provides an RS-232 serial interface to a breadboard 6502 computer, enabling more complex interactive programs.

Q: How do I set up the RS-232 serial interface? A: Connect the eight data lines, chip select, and register select lines of the 6551 chip to the appropriate address lines and decode logic of the breadboard 6502 computer.

Q: How do I initialize the 6551 chip? A: Use the control register to configure the baud rate, stop bits, word length, and other settings. You can also read the status register to determine the status of sending and receiving data.

Q: How do I receive data using the 6551 chip? A: Continuously monitor the receive data register full bit in the status register. When this bit is set, it means that an external device has sent data to the serial port of the breadboard 6502 computer.

Q: Can I send data using the 6551 chip? A: Yes, you can use the send character subroutine to set the character you want to send in the data register. Before sending each character, check the transmit data register empty bit to ensure proper transmission.

Q: How do I work around the hardware bug in the 6551 chip? A: Add a delay after sending each character to ensure that the transmit data register is fully emptied. The duration of the delay can be calculated based on the baud rate.

Q: Where can I find more information about the 6502 breadboard computer kits? A: Visit the eater.net 6502 website for kits, schematics, and additional resources.