diff --git a/02_boot_sequence/kickstart-boot-diagnostics.md b/02_boot_sequence/kickstart-boot-diagnostics.md index 3e15082..3f0629c 100644 --- a/02_boot_sequence/kickstart-boot-diagnostics.md +++ b/02_boot_sequence/kickstart-boot-diagnostics.md @@ -93,16 +93,39 @@ ExecOrigin: DC.W BIG_ROMS ; ROM identification ($1114) All diagnostic color constants are defined in `exec/constants.i` (lines 13–23). They use the Amiga's native 12-bit RGB format (`$0RGB`), written directly to the COLOR00 register at `$DFF180`. +#### 12-bit to 24-bit Color Conversion + +The Amiga stores color as a 16-bit word, but only the low 12 bits are used in OCS/ECS: four bits per channel (`$0RGB`). To convert each 4-bit nibble (0–F) to its 8-bit equivalent (0–255), multiply by 17: + +| 4-bit | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | A | B | C | D | E | F | +|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---| +| **8-bit** | `00` | `11` | `22` | `33` | `44` | `55` | `66` | `77` | `88` | `99` | `AA` | `BB` | `CC` | `DD` | `EE` | `FF` | + +The formula: `8bit_value = nibble × $11` (or `nibble × 17` in decimal). For example: + +| Amiga `$0RGB` | Breakdown | 24-bit `#RRGGBB` | Approximate Color | +|---|---|---|---| +| `$0000` | R=0, G=0, B=0 | `#000000` | Black | +| `$0111` | R=1, G=1, B=1 | `#111111` | Dark Grey | +| `$0F00` | R=F, G=0, B=0 | `#FF0000` | Red | +| `$00F0` | R=0, G=F, B=0 | `#00FF00` | Green | +| `$0FE5` | R=F, G=E, B=5 | `#FFEE55` | Yellow | +| `$0F0F` | R=F, G=0, B=F | `#FF00FF` | Magenta | +| `$000F` | R=0, G=0, B=F | `#0000FF` | Blue | +| `$0FFF` | R=F, G=F, B=F | `#FFFFFF` | White | + +> **AGA note:** The AGA chipset (A1200/A4000) extends COLOR00 to 24-bit (8 bits per channel) when `BPLCON3` bit `LOCT` = 1. In that mode the 12-bit conversion table above does not apply — each channel uses its full 8-bit value directly. Kickstart diagnostics always run in 12-bit mode since they execute before any AGA-specific setup. + ### 2.1 Progress Indicators (Normal Boot) These colors appear momentarily during a healthy boot, each signaling successful completion of a test phase. The grey intensifies as boot progresses — a deliberate design choice that gives the power-on sequence a visible "warming up" feel. | Constant | Value | Color | Meaning | When Set | |---|---|---|---|---| -| `OK_HARDWARE` | `$0111` | 🟫 Dark Grey | First software action after RESET | After disabling interrupts/DMA | -| `OK_SOFTWARE` | `$0888` | ⬜ Mid Grey | Chip RAM tests passed | After exception vector verify | -| `OK_RESLIST` | `$0AAA` | ⬜ Light Grey | All resident modules found | After `FindCodeBefore` | -| `OK_RESSTART` | `$0CCC` | ⬜ Bright Grey | About to start resident chain | Just before `InitCode` | +| `OK_HARDWARE` | `$0111` | Dark Grey | First software action after RESET | After disabling interrupts/DMA | +| `OK_SOFTWARE` | `$0888` | Mid Grey | Chip RAM tests passed | After exception vector verify | +| `OK_RESLIST` | `$0AAA` | Light Grey | All resident modules found | After `FindCodeBefore` | +| `OK_RESSTART` | `$0CCC` | Bright Grey | About to start resident chain | Just before `InitCode` | > **Design note:** In the production V40 ROM, only `OK_HARDWARE` survives — the intermediate grey stages (`OK_SOFTWARE`, `OK_RESLIST`, `OK_RESSTART`) were present in earlier revisions (visible in the RCS history of `constants.i`) but consolidated. The screen transitions from dark grey directly through to whatever the boot menu or Workbench draws. On a healthy machine, the grey flash is barely perceptible — lasting only the time it takes to checksum 512KB of ROM and verify chip RAM. @@ -112,17 +135,17 @@ When any test fails, the color is loaded into `D0` and execution branches to `co | Constant | Value | Color | Failure | Source Test | |---|---|---|---|---| -| `CC_BADROMSUM` | `$0F00` | 🟥 **Red** | Kickstart ROM checksum invalid | Additive wraparound-carry sum ≠ $FFFFFFFF | -| `CC_BADRAM` | `$00F0` | 🟩 **Green** | Chip memory not writable | Exception vector write-back verify failed | -| `CC_EXCEPTION` | `$0FE5` | 🟨 **Yellow** | CPU exception before software setup | Bus/Address error or illegal instruction | -| `CC_NOMODULES` | `$0F0F` | 🟪 **Purple** | `InitCode(RTF_COLDSTART)` returned | No bootable resident modules found | -| `CC_BADCHIPS` | `$000F` | 🟦 **Blue** | Custom chip register test failed | *(Commented out in V40 — was for early hardware)* | +| `CC_BADROMSUM` | `$0F00` | **Red** | Kickstart ROM checksum invalid | Additive wraparound-carry sum ≠ $FFFFFFFF | +| `CC_BADRAM` | `$00F0` | **Green** | Chip memory not writable | Exception vector write-back verify failed | +| `CC_EXCEPTION` | `$0FE5` | **Yellow** | CPU exception before software setup | Bus/Address error or illegal instruction | +| `CC_NOMODULES` | `$0F0F` | **Purple** | `InitCode(RTF_COLDSTART)` returned | No bootable resident modules found | +| `CC_BADCHIPS` | `$000F` | **Blue** | Custom chip register test failed | *(Commented out in V40 — was for early hardware)* | ### 2.3 Special Modes | Constant | Value | Color | Meaning | |---|---|---|---| -| `OK_DEBUG` | `$000F` | 🟦 Blue | Debug/development mode — fire button held at boot | +| `OK_DEBUG` | `$000F` | Blue | Debug/development mode — fire button held at boot | | `COLORON` | `$0200` | *(control)* | Written to `BPLCON0` to enable color burst output | ### 2.4 Color Progression Diagram @@ -131,7 +154,7 @@ When any test fails, the color is loaded into `D0` and execution branches to `co graph LR subgraph "Normal Boot Path" direction LR - A["RESET
⬛ Black"] --> B["OK_HARDWARE
$0111
🟫 Dark Grey"] + A["RESET
Black"] --> B["OK_HARDWARE
$0111
Dark Grey"] B --> C["ROM Checksum
Computing..."] C --> D["Vector Verify
Writing + Reading"] D --> E["ExecBase Built
Modules Found"] @@ -139,13 +162,13 @@ graph LR end subgraph "Failure Branches" - C -->|"Bad checksum"| R["CC_BADROMSUM
$0F00
🟥 RED"] - D -->|"Write failed"| G["CC_BADRAM
$00F0
🟩 GREEN"] - F -->|"No modules"| P["CC_NOMODULES
$0F0F
🟪 PURPLE"] + C -->|"Bad checksum"| R["CC_BADROMSUM
$0F00
RED"] + D -->|"Write failed"| G["CC_BADRAM
$00F0
GREEN"] + F -->|"No modules"| P["CC_NOMODULES
$0F0F
PURPLE"] end subgraph "Exception Path" - B -->|"CPU fault"| Y["CC_EXCEPTION
$0FE5
🟨 YELLOW"] + B -->|"CPU fault"| Y["CC_EXCEPTION
$0FE5
YELLOW"] end R --> CRASH["coldCrash
LED blink ×10
→ RESET"] @@ -541,13 +564,13 @@ This section maps observable symptoms to the specific source code paths that pro ```mermaid flowchart TD subgraph "Observable Symptoms" - BLACK["⬛ Black Screen
No brightness change"] - GREY["🟫 Grey Flash → Black"] - GREEN["🟩 Solid Green Screen
+ LED blinks"] - RED["🟥 Solid Red Screen
+ LED blinks"] - YELLOW["🟨 Yellow Screen
+ LED blinks"] - PURPLE["🟪 Purple Screen
Hangs"] - REDSYS["🟥 Red Screen with
device listing + text"] + BLACK["Black Screen
No brightness change"] + GREY["Grey Flash → Black"] + GREEN["Solid Green Screen
+ LED blinks"] + RED["Solid Red Screen
+ LED blinks"] + YELLOW["Yellow Screen
+ LED blinks"] + PURPLE["Purple Screen
Hangs"] + REDSYS["Red Screen with
device listing + text"] end subgraph "Source Code Path"