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millfork/docs/stdlib/nes.md

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# NES/Famicom-oriented modules
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## nes_hardware
The `nes_hardware` module is imported automatically on NES targets.
TODO
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## nes_mmc4
The `nes_mmc4` module is imported automatically on the NES MMC4 target.
and contains routines related to MMC4 bankswitching.
#### `void set_prg_bank(byte a)`
Changes the $8000-$BFFF PRG bank.
#### `void set_chr_bank0(byte a)`
Changes the CHR bank 0 ($0000-$0fff in the PPU memory space).
The high nibble (0 or 1) selects between `chrrom0` and `chrrom1` segments.
The low nibble L (0-$F) selects a 4K-aligned address in the segment ($L000).
#### `void set_chr_bank1(byte a)`
Changes the CHR bank 1 ($1000-$1fff in the PPU memory space).
The high nibble (0 or 1) selects between `chrrom0` and `chrrom1` segments.
The low nibble L (0-$F) selects a 4K-aligned address in the segment ($L000).
#### `void set_vertical_mirroring()`
Switches nametable mirroring to vertical.
#### `void set_horizontal_mirroring()`
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Switches nametable mirroring to horizontal.
## nes_joy
Provides an interface for reading joypads that is compatible with the `joy` module.
#### `alias input_a = input_btn`
1 if A button pressed, 0 id not pressed.
#### `byte input_b`
1 if B button pressed, 0 id not pressed.
#### `byte input_select`
1 if Select button pressed, 0 id not pressed.
#### `byte input_start`
1 if Start button pressed, 0 id not pressed.
#### `void read_joy1()`
Reads the joypad from the port 1.
#### `void read_joy2()`
Reads the joypad from the port 2.
#### `void read_also_joy1()`
Reads the joypad from the port 1 and adds its readouts to the current readouts.
#### `void read_also_joy2()`
Reads the joypad from the port 2 and adds its readouts to the current readouts.
#### `void nes_reset_joy()`
Resets the state variables.
Unlike `reset_joy`, this resets all the NES button states.
## nes_joy1_default
Defines the joystick in port 1 as the default joystick.
#### `alias read_joy = read_joy1`