When the Arduino Mega version arrived I added an SDCard+Ethernet Shield to it, as well as an LCD+Keypad shield (a standard Hitachi HD44780 LCD plus 6 push buttons). The LCD shield was required for operating the SDCard interface, e.g., browsing through files for PGM 1 (Load) and creating new files via PGM 2 (Save). It turned out that they didn't quite work together -I had to disconnect PIN 10 (I used extension headers and simply bent PIN 10 out of the way such that the LCD shield did not connect to it). I implemented the file operations using the String library and SDCard library. These two choices in libraries would cause major headaches later... see below.

The 6 push buttons on the shield were used for enter, cancel, and cursor movement. In addition, the 8 push buttons on the TM1638 were still being used for the Microtronic function keys.

I came up with the .MIC fileformat described in the Detail section above, and used an OCR program to scan programs from the Busch Microtronic Manuals. Suddenly, I had a large software library, with relatively little effort!

Running some larger programs I spotted some errors in the implementation of some instruction code - after all, I had reimplemented the virtual CPU based on the descriptions in the manuals, and the descriptions were incomplete and missleading in some cases (but only in 4). After a while of debugging I was able to run even the largest programs without differences from the documented behavior.

I figured it would be a shame to only use the LCD display for file operations, and hence implemented a CPU status display, showing register contents and a simple Mnemonics display during program editing etc. Very helpful for debugging.

The state of the emulator after Phase Two is represented by these videos: