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Description of DIAG options

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Diagnostics
--------
### DIAG
Progress through the boot and initialization process can be difficult to monitor
due to the lack of console or video output. Access to these output devices does
not become available until late the in the boot process. If these output devices
are also involved with the issue trying to be resolved then trouble shooting is
even more difficult.
ROMWBW can be configured to display boot progress with the assistance of additional
hardware. This take the form of an LED breakout debugging board connected to an
8-bit output port. As the boot code executes, the LED output display is updated.
To us an LED breakout board, it must be connected the computers data, reset and port
select lines.
To enable the DIAG option the following settings must be made in the systems .ini
configuration file, where 0xnn is the port address.
DIAGENABLE .SET TRUE
DIAGPORT .SET 0xnn
The following table shows the ROMWBW process steps in relation to the LED display.
| LED | ROMWBW Processes |
| -------- |:---------------------------------------------- |
| `........` | Initial boot |
| | Jump to start address |
| | Disable interrupts |
| | Set interrupt mode 1 |
| | Initialize critical ports and initial speed |
| `.......O` | Setup initial stack |
| | Memory manager and CPU configuration |
| | Set top bank to be RAM |
| `......OO` | Get and save battery condition |
| | Install HBIOS proxy in upper memory |
| | If platform is MBC reconfigure memory manager |
| | Setup "ROMLESS" HBIOS image or ... |
| | Copy HBIOS from ROM to RAM if RAM flag not set |
| | Jump to HBIOS in RAM |
| | Set running in RAM flag |
| `.....OOO` | Finalize configuration for running in RAM |
| | Check battery condition |
| | Check for recovery mode boot |
| `....OOOO` | Identify CPU type |
| `...OOOOO` | Set cpu oscillator speed |
| | Setup counter-timers |
| | Setup heap |
| `..OOOOOO` | Preconsole initialization |
| `.OOOOOOO` | Boot delay |
| | Set boot console device |
| | Bios announcement |
| `OOOOOOOO` | Display platform information |
| | Display memory configuration |
| | Display CPU family |
| | Verify ROM checksum |
| | Report battery condition |
| | Perform device driver initialization |
| | Report watchdog status |
| | Mark HBIOS heap so it is preserved |
| | Switch from boot console to CRT if active |
| | Display device summary |
| | Execute boot loader |
`\clearpage`{=latex}