Power On Startup Sequence

 On Power UP. (Something like this would happen)

  1. At power on the GPU/MMU maps the System and User ROMS into Super Block B this is a special block switch of a full 384K.
  2. The GPU/MMU sets the initial MMU blocks for CPU#0
  3. The GPU/MMU loads the Vector Table for CPU#0
  4. CPU#0 gets the RESET signal and runs the 6809 Master Power ON program.( See next section for details )
    4a. Simultaneously the GPU checks if a gif stored in a particular 18 blocks of NVRAM, If it finds the gif it starts rendering it otherwise it renders a hard coded fractal equation. on the VGA Base Screen and to the Composite Base Screen.
    If in Dual-CoCo Mode these screens will be visible until CoCo RED is ready.
    If in Tri-CoCo Mode these screens may not be visible.
    Also as part of the startup routine CPU#0 checks to see if "Factory Reset=TRUE" in settings.
  5. After the Executive Power ON Program completes the ROMs are swapped back out and the CPU#0 starts the Executive supervisory program.


The Executive Power ON program.

  1. CPU#0 checks settings memory to determine if system is to run in Dual-CoCo or Tri-CoCo mode.

  2. Based on settings memory entrys and 3/4 switch position CPU#0 initiates a GPU-BLOCK-COPY of the ROMs to be the ShareALL Superblock D and then starts copying the ROM for CPU#2 to the Home Memory of CPU#2 in Superblock G if CoCo2 mode or otherwise to an available space in SharedALL  Superblock D .
  3. The Superblock B RAM is returned to the CPU accessible area and the ROMS are returned to the hidden memory(That only the GPU can access.).
  4. The Vector Table for CPU#2 is loaded and CPU#2 boots from this ROM as CoCo Green.
  5. Depending on settings CoCo Green's screen will either display on a section of the VGA monitor or be hidden in the background. or displayed on the composite monitor.
  6. If  hidden in the background a message will display at the bottom of the screen in the Executive Supervisory Program interface area COCO GREEN READY !
  7. Finally the final CPU is ready to come online.



  8. The Executive Power ON program then starts the Executive Supervisory program and stays in the background to monitor the Power and RESET buttons.
    Now we have fully started with only a 1/4 to 3 Second delay over a CoCo 3.

Extra Info:

To Illustrate what goes on with memory at startup. See where the "ROM" is temporary mapped in.

And then then mapped back out.

  The ROM is now mapped back out of memory and can only be re-accessed by a X>RESET ALL OFF or  X>RESET FULL POWER CYCLE which has been indicated by flipping the text "System R.O.M." and "User E.E.P.R.O.M." upside down.