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@ -12,22 +12,27 @@ GBA game, so it's a good starting one to go over for that reason too.
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The display control register holds a `u16` value, and is located at `0x0400_0000`.
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Many of the bits here won't mean much to you right now. **That is fine.** You do
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NOT need to memorize them all or what they all do right away. We'll just skim
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over all the parts of this register to start, and then we'll go into more detail
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in later chapters when we need to come back and use more of the bits.
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## Video Modes
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The lowest three bits (0-2) let you select from among the GBA's six video modes.
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You'll notice that 3 bits allows for eight modes, but the values 6 and 7 are
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prohibited.
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Modes 0, 1, and 2 are "Tiled" modes. These are actually the modes that you
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Modes 0, 1, and 2 are "tiled" modes. These are actually the modes that you
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should eventually learn to use as much as possible. It lets the GBA's limited
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video hardware do as much of the work as possible, leaving more of your CPU time
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for gameplay computations. However, they're also complex enough to deserve their
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own demos and chapters later on, so that's all we'll say about them for now.
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Modes 3, 4, and 5 are "Bitmap" modes. These let you write individual pixels to
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Modes 3, 4, and 5 are "bitmap" modes. These let you write individual pixels to
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locations on the screen.
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* **Mode 3** is full resolution (240w x 160h) RBG15 color. You might not be used
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* **Mode 3** is full resolution (240w x 160h) RGB15 color. You might not be used
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to RGB15, since modern computers have 24 or 32 bit colors. In RGB15, there's 5
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bits for each color channel stored within a `u16` value, and the highest bit is
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simply ignored.
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@ -64,7 +69,9 @@ Bit 5 lets you access OAM during HBlank if enabled. This is cool, but it reduces
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the maximum sprites per scanline, so it's not default.
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Bit 6 lets you adjust if the GBA should treat Object Character VRAM as being 2d
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(off) or 1d (on).
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(off) or 1d (on). This particular control can be kinda tricky to wrap your head
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around, so we'll be sure to have some extra diagrams in the chapter that deals
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with it.
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Bit 7 forces the screen to stay in vblank as long as it's set. This allows the
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fastest use of the VRAM, Palette, and Object Attribute Memory. Obviously if you
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@ -145,19 +145,23 @@ that we can get a hint of what's to come.</p>
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<p>Also it's the one that you basically always need to set at least once in every
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GBA game, so it's a good starting one to go over for that reason too.</p>
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<p>The display control register holds a <code>u16</code> value, and is located at <code>0x0400_0000</code>.</p>
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<p>Many of the bits here won't mean much to you right now. <strong>That is fine.</strong> You do
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NOT need to memorize them all or what they all do right away. We'll just skim
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over all the parts of this register to start, and then we'll go into more detail
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in later chapters when we need to come back and use more of the bits.</p>
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<a class="header" href="#video-modes" id="video-modes"><h2>Video Modes</h2></a>
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<p>The lowest three bits (0-2) let you select from among the GBA's six video modes.
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You'll notice that 3 bits allows for eight modes, but the values 6 and 7 are
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prohibited.</p>
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<p>Modes 0, 1, and 2 are "Tiled" modes. These are actually the modes that you
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<p>Modes 0, 1, and 2 are "tiled" modes. These are actually the modes that you
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should eventually learn to use as much as possible. It lets the GBA's limited
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video hardware do as much of the work as possible, leaving more of your CPU time
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for gameplay computations. However, they're also complex enough to deserve their
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own demos and chapters later on, so that's all we'll say about them for now.</p>
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<p>Modes 3, 4, and 5 are "Bitmap" modes. These let you write individual pixels to
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<p>Modes 3, 4, and 5 are "bitmap" modes. These let you write individual pixels to
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locations on the screen.</p>
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<ul>
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<li><strong>Mode 3</strong> is full resolution (240w x 160h) RBG15 color. You might not be used
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<li><strong>Mode 3</strong> is full resolution (240w x 160h) RGB15 color. You might not be used
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to RGB15, since modern computers have 24 or 32 bit colors. In RGB15, there's 5
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bits for each color channel stored within a <code>u16</code> value, and the highest bit is
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simply ignored.</li>
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@ -186,7 +190,9 @@ the 0th page is used, and when the bit is 1 the 1st page is used.</p>
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<p>Bit 5 lets you access OAM during HBlank if enabled. This is cool, but it reduces
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the maximum sprites per scanline, so it's not default.</p>
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<p>Bit 6 lets you adjust if the GBA should treat Object Character VRAM as being 2d
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(off) or 1d (on).</p>
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(off) or 1d (on). This particular control can be kinda tricky to wrap your head
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around, so we'll be sure to have some extra diagrams in the chapter that deals
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with it.</p>
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<p>Bit 7 forces the screen to stay in vblank as long as it's set. This allows the
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fastest use of the VRAM, Palette, and Object Attribute Memory. Obviously if you
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leave this on for too long the player will notice a blank screen, but it might
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|
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@ -499,19 +499,23 @@ that we can get a hint of what's to come.</p>
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<p>Also it's the one that you basically always need to set at least once in every
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GBA game, so it's a good starting one to go over for that reason too.</p>
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<p>The display control register holds a <code>u16</code> value, and is located at <code>0x0400_0000</code>.</p>
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<p>Many of the bits here won't mean much to you right now. <strong>That is fine.</strong> You do
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NOT need to memorize them all or what they all do right away. We'll just skim
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over all the parts of this register to start, and then we'll go into more detail
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in later chapters when we need to come back and use more of the bits.</p>
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<a class="header" href="#video-modes" id="video-modes"><h2>Video Modes</h2></a>
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<p>The lowest three bits (0-2) let you select from among the GBA's six video modes.
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You'll notice that 3 bits allows for eight modes, but the values 6 and 7 are
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prohibited.</p>
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<p>Modes 0, 1, and 2 are "Tiled" modes. These are actually the modes that you
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<p>Modes 0, 1, and 2 are "tiled" modes. These are actually the modes that you
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should eventually learn to use as much as possible. It lets the GBA's limited
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video hardware do as much of the work as possible, leaving more of your CPU time
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for gameplay computations. However, they're also complex enough to deserve their
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own demos and chapters later on, so that's all we'll say about them for now.</p>
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<p>Modes 3, 4, and 5 are "Bitmap" modes. These let you write individual pixels to
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<p>Modes 3, 4, and 5 are "bitmap" modes. These let you write individual pixels to
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locations on the screen.</p>
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<ul>
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<li><strong>Mode 3</strong> is full resolution (240w x 160h) RBG15 color. You might not be used
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<li><strong>Mode 3</strong> is full resolution (240w x 160h) RGB15 color. You might not be used
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to RGB15, since modern computers have 24 or 32 bit colors. In RGB15, there's 5
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bits for each color channel stored within a <code>u16</code> value, and the highest bit is
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simply ignored.</li>
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@ -540,7 +544,9 @@ the 0th page is used, and when the bit is 1 the 1st page is used.</p>
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<p>Bit 5 lets you access OAM during HBlank if enabled. This is cool, but it reduces
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the maximum sprites per scanline, so it's not default.</p>
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<p>Bit 6 lets you adjust if the GBA should treat Object Character VRAM as being 2d
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(off) or 1d (on).</p>
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(off) or 1d (on). This particular control can be kinda tricky to wrap your head
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around, so we'll be sure to have some extra diagrams in the chapter that deals
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with it.</p>
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<p>Bit 7 forces the screen to stay in vblank as long as it's set. This allows the
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fastest use of the VRAM, Palette, and Object Attribute Memory. Obviously if you
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leave this on for too long the player will notice a blank screen, but it might
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|
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