The serial interrupt code in the factory ECU utilizes a simple request-response protocol. A 1-byte hexadecimal address is sent to the ECU, which responds with the contents of the RAM at that specific memory address.

Serial Communication Limitations#

The factory ECU serial port is initialized at a high baud rate, calculated as (CLK / 64). At a clock speed of 12MHz, this results in a baud rate of 187,500. This frequency is incompatible with standard PC serial ports.

Important

Refer to the Intel 80510 documentation for detailed specifications regarding the serial port hardware and clock configuration.

Implementing Datalogging#

To enable functional datalogging with standard PC hardware, the Timer2 peripheral—which remains unused in the factory firmware—is repurposed. By configuring Timer2, the serial port can be initialized to a standard 9600 baud rate, allowing for reliable communication between the ECU and a PC.

Technical Requirements#

• Protocol: 1-byte hex address request.
• Standard Baud Rate: 9600 bps.
• Hardware Resource: Timer2 (repurposed for baud rate generation).

{{> serial-communication-notes }}