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#+TITLE: Terminology
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#+AUTHOR: Riyyi
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#+LANGUAGE: en
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#+OPTIONS: toc:nil
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GameBoy terminology.
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** Terminology
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*** Hardware
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| Name | Modern equivalent | Description |
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|-----------------+-------------------+-------------------------------------------|
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| APU | Sound card | Audio Processing Unit |
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| PPU | GPU | Pixel Processing Unit |
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| Bootrom | BIOS | |
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| HRAM (High RAM) | CPU cache | Embedded memory inside the CPU, 127 bytes |
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| WRAM (Work RAM) | RAM | |
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*** Flags
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The Half Cary (H) flag differs between 8-bit or 16-bit operations. The 8-bit
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variant indicates carry for the lower 4 bits of the result, or overflow from bit
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4 to bit 5. The 16-bit variant indicates carry for the lower 4 bits of the
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*second* byte of the result, or overflow from bit 12 to bit 13.
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*** Opcode
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| Name | Bits | Sign | Mnemonics | [[https://gbdev.io/gb-opcodes/optables/][1]] | [[https://rgbds.gbdev.io/docs/v0.5.2/gbz80.7/][2]] | [[https://gekkio.fi/files/gb-docs/gbctr.pdf][3]]/[[http://marc.rawer.de/Gameboy/Docs/GBCPUman.pdf][3]] | [[https://gbdev.io/pandocs/CPU_Instruction_Set.html][4]] | Description | Note |
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|-----------+------+----------+-----------+------+-----+------+-----+------------------------------+-------------------|
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| | | | | <r> | <r> | <r> | <r> | | |
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| immediate | 8 | unsigned | i8 | d8 | n8 | n | | Next byte in memory | |
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| immediate | 16 | unsigned | i16 | d16 | n16 | nn | | Next byte in memory | little-endian |
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| register | 8 | unsigned | r8 | | r8 | r | | Any of the registers | |
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| register | 16 | unsigned | r16 | | r16 | rr | | Any of the registers | little-endian |
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| address | 8 | unsigned | a8 | | | (n) | | Address at value | |
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| address | 16 | unsigned | a16 | a16 | n16 | (nn) | nn | Address at value | little-endian |
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| immediate | 8 | signed | s8 | r8 | e8 | e | dd | Next byte in memory | |
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| immediate | 8 | unsigned | io8 | (a8) | n16 | (n) | n | 0xff00 + next byte in memory | write to I/O-port |
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| condition | | | <ZNHC> | NZ | cc | | f | Execute if condition met | |
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d = data \\
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n = constant
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*** Variables
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| Name | Meaning |
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|--------+--------------------|
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| length | amount of elements |
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| size | amount of bytes |
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|--------+--------------------|
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| lhs | left hand side |
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| rhs | right hand side |
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** References
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- https://gbdev.io/pandocs/Memory_Map.html
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- https://gbdev.io/pandocs/Specifications.html
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