Tiny030 at stage 3 is a fully functional computer.  I have developed a simple ROM monitor previously for 680x0 board so with small modification, it is suitable as Tiny030 ROM monitor.  As a monitor, it has the basic functions of display/modify memory, display/modify registers, load S-records, and execute program.  It communicates with the terminal program at 38400-N-8-1, no handshake.  It also perform basic I/O using TRAP15 calls compatible with EASy68K simulator, so a program can be simulated first with EASySIM and then load & execute in Tiny030 without modifications.  A 'he' command display the menu as follow:

As a state-of-health indicator, the 7-segment LED displays the various state of the monitor software as it boots up and a rotating LED segments during idle state.  

Since the address map of the RAM has changed since Stage 2, the memory diagnostic need to relocate to the new base address.  It is loaded & executed with the Tiny030 monitor.

The memory diagnostic passes, so now I'm ready to load the EhBASIC which also need to be modified slightly to accommodate the different memory map between stage 2 and stage 3 hardware.  Once EhBASIC is loaded, I load up the mandelbrot program and run it.

So Stage 3 Tiny030 has a functioning ROM monitor.  It passes memory diagnostic, and it can run real applications like EhBASIC.  We are ready to go to Stage 4.