Data General microNOVA Console Debug Interface

The Data General microNOVA can be outfitted with an Async card with a Console Debug ROM that provides a memory monitor interface. This allows directly reading and writing to memory, executing instructions, and setting break points directly over a serial interface.

This would make it possible to fully interface with the computer and peripherals from a modern computer with just a USB serial adapter.

The Project

The purpose of this software is to provide a software front-end to the Console Debug to control it from a modern computer. The primary goals are as follows:

• Read Memory: Be able to dump regions of memory directly over serial.
• Load Software: Write software directly into memory to run it.
• Receive Data: Software running on the computer could transfer data to a modern system.
• Debug: If sufficient development tools are created on a modern system it would be possible to use the Debug features when developing software. This may be possible to implement as a Gdbserver.

microNOVA System Notes

• Octal: The microNOVA Console Debug interface uses an Octal syntax, that is values are represented from 0-7. I will be indicating these values with a prefix of 0o. For example, the number 12 would be 0o15.

References

• microNOVA Programmers Reference
• • Page 45: The operation of the console debug interface
• microNOVA Technical Reference
• • Page 14: The console debug ROM resides in address range 0o77400-0o77777

Console Debug Commands

The console has two main states, "waiting" and "displaying a value". All commands are entered as a postfix after a value, if you are in the "waiting" state you will need to enter a value first. The Console Debug interface can also do addition and subtraction on any inputs used for values or addresses.

Only one breakpoint may be set at a time.

"n" represents a value or address and capitalization of commands matters

• n A: Reads internal CPU register
• n /: Reads the contents of a memory address and opens it for editing
• n [Carriage Return]: Enters n value into the last displayed value as an address, the goes back to waiting.
• n [New Line]: Enters n value into the last displayed value as an address, then displays value of next address.
• n B: Sets breakpoint at address
• D: Remove breakpoint
• n R: Begins execution starting at given address
• P: Resume execution if interrupted
• n L: Loads program from given device code and executes it
• K: Cancel current entry and returns to waiting