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02_boot_sequence/cold_boot.md
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@ -209,11 +209,11 @@ while ((cd = FindConfigDev(cd, -1, -1)) != NULL)
## Step 5: ROM Self-Test and Diagnostic Indicators
The Amiga has a multi-layered diagnostic system that uses screen colours, power LED patterns, and keyboard LED blink codes to communicate status. Understanding these signals is essential for FPGA core development and hardware debugging.
The Amiga has a multi-layered diagnostic system that uses screen colors, power LED patterns, and keyboard LED blink codes to communicate status. Understanding these signals is essential for FPGA core development and hardware debugging.
### Normal Boot Colour Sequence
### Normal Boot Color Sequence
A healthy boot cycles through these colours rapidly (total <1 second on 68000):
A healthy boot cycles through these colors rapidly (total <1 second on 68000):
```
┌─────────┐ ┌──────────┐ ┌───────────┐ ┌───────────┐ ┌──────────┐ ┌─────────┐
@ -223,16 +223,16 @@ A healthy boot cycles through these colours rapidly (total <1 second on 68000):
└─────────┘ └──────────┘ └───────────┘ └───────────┘ └──────────┘ └─────────┘
```
If the sequence **stops** at any colour, that colour identifies the failure point.
If the sequence **stops** at any color, that color identifies the failure point.
### Screen Colour Diagnostic Table
### Screen Color Diagnostic Table
| Colour | Hex | Phase | Indicates | What Failed |
| Color | Hex | Phase | Indicates | What Failed |
|---|---|---|---|---|
| Black (stuck) | `$000` | Pre-init | CPU not executing | No clock, dead CPU, no ROM addressing |
| Dark grey | `$444` | Post-checksum | ROM checksum passed | (Normal — transient) |
| Medium grey | `$888` | Memory test | Chip RAM sized OK | (Normal — transient) |
| Light grey | `$AAA` | Exec init | ExecBase created | (Normal — transient) |
| Dark gray | `$444` | Post-checksum | ROM checksum passed | (Normal — transient) |
| Medium gray | `$888` | Memory test | Chip RAM sized OK | (Normal — transient) |
| Light gray | `$AAA` | Exec init | ExecBase created | (Normal — transient) |
| White | `$FFF` | Resident scan | Modules initializing | (Normal — transient) |
| Green flash | `$0F0` | DOS boot | dos.library starting | (Normal — transient) |
| **Red** (stuck) | `$F00` | **Checksum** | **ROM checksum failed** | Bad ROM chip, wrong image, bit rot |
@ -242,17 +242,17 @@ If the sequence **stops** at any colour, that colour identifies the failure poin
| **Magenta** (stuck) | `$F0F` | **Exception** | **Hardware trap** | Unexpected interrupt or bus error |
| **Cyan** (stuck) | `$0FF` | **Misc** | **CIA or clock** | Timer initialization failure |
### How the ROM Sets Diagnostic Colours
### How the ROM Sets Diagnostic Colors
```asm
; The boot code writes COLOR00 at each milestone:
; After ROM checksum passes:
MOVE.W #$0444,$DFF180 ; Dark grey → "ROM OK"
MOVE.W #$0444,$DFF180 ; Dark gray → "ROM OK"
; After Chip RAM test passes:
MOVE.W #$0888,$DFF180 ; Medium grey → "RAM OK"
MOVE.W #$0888,$DFF180 ; Medium gray → "RAM OK"
; On failure — set error colour and halt:
; On failure — set error color and halt:
RomChecksumFailed:
MOVE.W #$0F00,$DFF180 ; Red screen
.hang:
@ -264,7 +264,7 @@ RamTestFailed:
BRA.S .hang
```
### Power LED Behaviour
### Power LED Behavior
| Pattern | Meaning |
|---|---|
@ -290,15 +290,15 @@ The Amiga keyboard has its own 6500/1 microcontroller that performs a self-test
The keyboard communicates with the main system via a synchronous serial protocol through CIA-A. If the keyboard passes self-test, it sends a power-up key stream (`$FD` = initiate power-up, then `$FE` = terminate power-up).
### Normal vs Abnormal Boot Behaviour
### Normal vs Abnormal Boot Behavior
**Normal boot** (A500/A1200 with Kickstart 3.1):
```
0 ms: Black screen
~5 ms: Dark grey (ROM checksum calculating)
~600 ms: Medium grey (checksum done, RAM test running)
~650 ms: Light grey (ExecBase init)
~5 ms: Dark gray (ROM checksum calculating)
~600 ms: Medium gray (checksum done, RAM test running)
~650 ms: Light gray (ExecBase init)
~700 ms: White (resident scan starting)
~900 ms: Colors flash rapidly (graphics.library init, display setup)
~1.2 s: Kickstart hand/checkmark animation appears