46 lines
3.0 KiB
Markdown
46 lines
3.0 KiB
Markdown
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## Main RAM
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8 KiB of random-access memory.<br>
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Located at addresses `$8000` to `$9FFF`.<br>
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Programs can write data to these addresses, and retrieve the data at a later time.<br>
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Machine code can also be stored here and executed.
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## Text Display
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Write ASCII values to addresses `$2000` to `$27FF` to display characters at certain positions on the screen.<br>
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`$2000` is the top left, `$27FF` is the bottom right.<br>
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Rows are 64 bytes long.<br>
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For example, `$2040` would be the first character of the second row from the top.<br>
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Values can also be read back out of the display memory, as if it were RAM.
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## Text Display Color
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Write 6-bit color IDs to addresses `$0C00` to `$0FFF` to set the color of characters on the screen.<br>
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If the most significant bit is 1, the character and background colors will be inverted, i.e. highlighted.<br>
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Values can also be read back out of the display color memory, as if it were RAM.
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## Main ROM
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1 KiB of read-only memory.<br>
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Located at addresses `$0000` to `$03FF`.<br>
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When the CPU is first turned on, or is reset, it will start executing code from here, starting at address `$0000`.<br>
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Bricks can be physically placed on top of the ROM brick to set bits within the ROM.<br>
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A bootloader, operating system, or hex monitor may be loaded here.
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## GPIO
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Contains hardware multiplication, division, popcount, and a timer.<br>
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When two 8-bit values are written to the multiplier registers `$0400` and `$0401`, the result will be available as a big-endian 16-bit value at `$0400`. Read from `$0401` to retrieve an 8-bit result.<br>
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When two 8-bit values are written to the divider registers `$0402` and `$0403`, the quotient can be read from `$0402` and the remainder from `$0403`<br>
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When any 8-bit value is written to the timer register `$0404`, the popcount of that value (The number of bits that are 1) can be read from the same location.
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When any value is written to the timer register at `$0405`, an interrupt will be triggered after 32 milliseconds.
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## Keyboard
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Read address `$0500` to get the next keycode from the buffer.<br>
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Keycodes are 7-bit Windows VKey codes, plus a press/release bit. If the MSB is 1, the event is a key press; if 0, a release.<br>
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Result will be 0 if the buffer is empty.<br>
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If 1 is written to `$0500`, an interrupt will be triggered whenever a key event is available. Write 0 to disable again.
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## Robot Controller
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Write to `$0701` to control a 1x1f-sized "robot" that can place and destroy bricks.<br>
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Each bit indicates an action; if that bit is set, that action will be taken. From MSB to LSB: Plant brick, destroy brick, move forward, backward, left, right, up, down.<br>
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Write a 6-bit color ID to `$0700` to set the color of the bricks the robot will plant.<br>
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Read `$0700` to get the color of the brick the robot is currently overlapping. If the MSB is 1, a brick exists at this location. Result will be 0 if no brick is present.<br>
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The robot should only be given new actions once per game tick. The timer at `$0405` can be used for this purpose.
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