rslr/amiga-bootcamp
1
0
Fork 0
mirror of https://github.com/alfishe/amiga-bootcamp.git synced 2026-06-13 00:26:28 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

docs: minor updates to zorro_bus, game_reversing, expansion

Browse source
This commit is contained in:
Ilia Sharin 2026-05-12 22:04:26 -04:00
parent 9f5d9de1ed
commit 7960cbdf25
3 changed files with 9 additions and 120 deletions
Download patch file Download diff file Expand all files Collapse all files

29
11_libraries/expansion.md
View file

@ -88,34 +88,9 @@ The system requires no handshake signal — once the base address is written, th
The board presents its identity at the configuration address. Each logical byte is read via **two even-address accesses** (nibble-pair format): the high nibble from bits `D7–D4` at `offset`, the low nibble from bits `D7–D4` at `offset + 2`. This allows boards to use cheap 4-bit PROMs. All fields except `er_Type` are stored **inverted** in the ROM (XOR `$FF`) — an empty bus reads `$FF`, which inverts to `$00`, cleanly signaling "no more boards."
See [AutoConfig Protocol — Nibble-Pair Format](../01_hardware/common/autoconfig.md#the-nibble-pair-format--logical-inversion) for the full physical-to-logical address map.
The ROM encodes bus type (Zorro II vs III), memory vs I/O classification, board size, manufacturer ID (16-bit), product ID (8-bit), serial number (32-bit), and an optional DiagArea vector. The lower nibble of `er_Type` is a size code that maps to different byte sizes on Zorro II and Zorro III.
| Offset | Register | Bits | Description |
|---|---|---|---|
| $00 | `er_Type` | 7:6 | Board type: `11`=Zorro II, `10`=Zorro III |
| $00 | `er_Type` | 5 | Memory board (1) or I/O board (0) |
| $00 | `er_Type` | 4 | Chain bit — more boards follow |
| $00 | `er_Type` | 3:0 | Size code (see table below) |
| $02 | `er_Product` | 7:0 | Product number (0–255) |
| $04 | `er_Flags` | 7 | Can be shut up (mapped out) |
| $04 | `er_Flags` | 5 | Board's memory is free (add to system pool) |
| $04 | `er_Flags` | 4 | `er_InitDiagVec` is valid (`ERFB_DIAGVALID`) |
| $08/$0A | `er_Manufacturer` | 15:0 | Manufacturer ID (assigned by Commodore) |
| $0C–$12 | `er_SerialNumber` | 31:0 | Serial number (unique per board) |
| $20/$22 | `er_InitDiagVec` | 15:0 | Offset to optional boot ROM (DiagArea) |
### Size Code
| Code | Zorro II Size | Zorro III Size |
|---|---|---|
| $0 | 8 MB | 16 MB |
| $1 | 64 KB | 32 MB |
| $2 | 128 KB | 64 MB |
| $3 | 256 KB | 128 MB |
| $4 | 512 KB | 256 MB |
| $5 | 1 MB | 512 MB |
| $6 | 2 MB | 1 GB |
| $7 | 4 MB | — |
See [AutoConfig Protocol — Data Structures & Register Tables](../01_hardware/common/autoconfig.md#data-structures--register-tables) for the complete ROM layout, size code matrix, and `er_Flags` bit definitions.
---