Doc: Add document that describes the GameBoy terminology

The 8 lower bits are read first. The 8 higher bits come afterwards!

doc/terminology.org

@@ -0,0 +1,46 @@
+#+TITLE: Terminology
+#+AUTHOR: Riyyi
+#+LANGUAGE: en
+#+OPTIONS: toc:nil
+
+GameBoy terminology.
+
+** Terminology
+
+*** Hardware
+
+https://gbdev.io/pandocs/Specifications.html
+https://gbdev.io/pandocs/Memory_Map.html
+
+| Name            | Modern equivalent | Description                               |
+|-----------------+-------------------+-------------------------------------------|
+| APU             |                   | Audio Processing Unit                     |
+| PPU             | GPU               | Pixel Processing Unit                     |
+| Bootrom         | BIOS              |                                           |
+| HRAM (High RAM) | CPU cache         | Embedded memory inside the CPU, 127 bytes |
+| WRAM (Work RAM) | RAM               |                                           |
+
+*** Opcode
+
+| Name      | Bits | Sign     | Mnemonics |    1 |   2 |    3 |   4 | Description                  | Note              |
+|-----------+------+----------+-----------+------+-----+------+-----+------------------------------+-------------------|
+|           |      |          |           |  <r> | <r> |  <r> | <r> |                              |                   |
+| immediate |    8 | unsigned |           |   d8 |  n8 |    n |     | Next byte in memory          |                   |
+| immediate |   16 | unsigned |           |  d16 | n16 |   nn |     | Next byte in memory          | little-endian     |
+| register  |    8 | unsigned |           |      |  r8 |    r |     | Any of the registers         |                   |
+| register  |   16 | unsigned |           |      | r16 |   rr |     | Any of the registers         | little-endian     |
+| address   |    8 | unsigned |           |      |     |  (n) |     | Address at value             |                   |
+| address   |   16 | unsigned |           |  a16 | n16 | (nn) |  nn | Address at value             | little-endian     |
+| immediate |    8 | signed   |           |   r8 |  e8 |    e |  dd | Next byte in memory          |                   |
+| immediate |    8 | unsigned |           | (a8) | n16 |  (n) |   n | 0xff00 + next byte in memory | write to I/O-port |
+| condition |      |          |           |   NZ |  cc |      |   f | Execute if condition met     |                   |
+
+d = data
+n = constant
+
+*** Variables
+
+| Name   | Meaning            |
+|--------+--------------------|
+| size   | amount of bytes    |
+| length | amount of elements |

src/cpu.h

@@ -55,7 +55,7 @@ private:
 	uint8_t peekMemory(int32_t offset = 0) const;
 	uint8_t consumeMemory();
 
-	uint32_t immediate16() { return (consumeMemory() << 8) | consumeMemory(); }
+	uint32_t immediate16() { return consumeMemory() | (consumeMemory() << 8); }
 
 	void setBc(uint32_t value);
 	void setDe(uint32_t value);

src/main.cpp

@@ -8,6 +8,7 @@
 #include "cpu.h"
 #include "emu.h"
 #include "ppu.h"
+#include "ruc/file.h"
 #include "ruc/format/print.h"
 #include "ruc/timer.h"
 
@@ -40,6 +41,17 @@ int main(int argc, char* argv[])
 	Emu::the().addMemorySpace("OAM", 0xfe00, 0xfe9f, 1);     // 160B, Object Attribute Memory (VRAM Sprite Attribute Table)
 	Emu::the().addMemorySpace("HRAM", 0xff80, 0xfffe, 1);    // 127B, High RAM (CPU cache)
 
+	// Load bootrom
+	auto bootrom = ruc::File("gbc_bios.bin").data();
+	for (size_t i = 0; i < bootrom.length(); ++i) {
+		// Skip cartridge header memory range
+		if (i >= 0x0100 && i <= 0x01ff) {
+			continue;
+		}
+
+		Emu::the().writeMemory(i, bootrom[i]);
+	}
+
 	// Get shared register
 	print("{}\n", *Emu::the().processingUnit("cpu")->sharedRegister("a"));
 	print("{}\n", *Emu::the().processingUnit("cpu")->sharedRegister("b"));