Pan Docs

https://gbdev.io/pandocs
Admin
The single most comprehensive technical reference to Game Boy available to the public, providing...
Tokens:195,302
Snippets:1,656
Trust Score:9.1
Update:4 months ago
Show doc for...
Tokens:
Raw
### Print Job Sequence Example

Source: https://gbdev.io/pandocs/Gameboy_Printer.html

A step-by-step example of how to initiate and monitor a print job.

```Assembly
Send command 1, the answer should be $81, $00
Send command 4 with $280 of your graphics, the answer should still be $81, $00
Ask for status with command $F, the answer should now be $81, $08 (ready to print)
Send an empty command 4 packet, the answer should still be $81, $08
Send command 2 with your arguments (margins, palette, exposure), the answer should still be $81, $08
Ask for status with command $F until it changes to $81, $06 (printing !)
Ask for status with command $F until it changes to $81, $04 (printing done)
Optionally send 16 zero bytes to clear the printer’s receive buffer (GB Camera does it)
```

--------------------------------

### Instruction Grouping Example

Source: https://gbdev.io/pandocs/print.html

Illustrates how instructions performing similar operations with different parameters can be grouped, using 'inc r16' as an example.

```text
inc bc
inc de
inc hl
inc sp
```

--------------------------------

### Enable Rumble

Source: https://gbdev.io/pandocs/MBC5.html

Example of enabling the rumble motor.

```assembly
ld a, $01
ldh [rJOYP], a
```

--------------------------------

### Wisdom Tree Mapper - Initialization Code Example

Source: https://gbdev.io/pandocs/single.html

Example code to be placed at $0100 in all banks but the first, for handling interrupt vectors and bank switching with the Wisdom Tree mapper.

```assembly
; At $0100 in all banks but the first
    nop
    jp $7FFB

```

--------------------------------

### Pokémon Pinball Rumble Control Example

Source: https://gbdev.io/pandocs/print.html

Examples from Pokémon Pinball demonstrating how to control the rumble motor's intensity by repeatedly turning it on and off.

```c
#define RUMBLE_ON 1
#define RUMBLE_OFF 0

void controlRumbleIntensity(int intensityLevel) {
    // Simplified example: intensityLevel could map to number of on/off cycles
    if (intensityLevel > 0) {
        // Turn rumble on
        // Write to rumble control register (e.g., 0x2000, bit 3)
        // ...
        
        // Wait for a short duration (simulated)
        // ... 
        
        // Turn rumble off
        // Write to rumble control register (e.g., 0x2000, bit 3)
        // ...
    }
}
```

--------------------------------

### Wisdom Tree Mapper - Bank Switching Routine Example

Source: https://gbdev.io/pandocs/single.html

Example code for the bank switching routine at $7FFB, used in conjunction with the Wisdom Tree mapper.

```assembly
; At $7FFB in all banks
    ld hl, $0100
    ld [hl], a
    jp hl

```

--------------------------------

### Ping Packet Examples

Source: https://gbdev.io/pandocs/Four_Player_Adapter.html

Examples of ping packets sent by the DMG-07, illustrating different connection statuses.

```text
FE 01 01 01
FE 11 11 11
FE 31 31 31
FE 71 71 71
FE 62 62 62
```

--------------------------------

### PAL03 Command Example

Source: https://gbdev.io/pandocs/print.html

Same as PAL01, but for Palettes 0 and 3 respectively. The header byte is $11.

```assembly
Same as `PAL01` above, but for Palettes 0 and 3 respectively. The **header** byte is thus $11.
```

--------------------------------

### Wisdom Tree Mapper - Initialization Code

Source: https://gbdev.io/pandocs/print.html

Example code to be placed at $0100 in all banks but the first for the Wisdom Tree mapper.

```Assembly
; At $0100 in all banks but the first
    nop
    jp $7FFB
```

--------------------------------

### PAL12 Command Example

Source: https://gbdev.io/pandocs/print.html

Same as PAL01, but for Palettes 1 and 2 respectively. The header byte is $19.

```assembly
Same as `PAL01` above, but for Palettes 1 and 2 respectively. The **header** byte is thus $19.
```

--------------------------------

### PAL23 Command Example

Source: https://gbdev.io/pandocs/print.html

Same as PAL01, but for Palettes 2 and 3 respectively. The header byte is $09.

```assembly
Same as `PAL01` above, but for Palettes 2 and 3 respectively. The **header** byte is thus $09.
```

--------------------------------

### Good VBlank Wait Example using HALT

Source: https://gbdev.io/pandocs/Reducing_Power_Consumption.html

An efficient method of waiting for VBlank using the HALT instruction and a flag.

```asm
__
  ld   hl, vblank_flag  ; hl = pointer to vblank_flag
  xor  a                ; a = 0
.wait
  halt                  ; suspend CPU - wait for ANY enabled interrupt
  cp   a, [hl]          ; is the vblank_flag still zero?
  jr   z, .wait         ; keep waiting if zero
  ld   [hl], a          ; set the vblank_flag back to zero


```

--------------------------------

### EMS Mapper Game Startup Sequence

Source: https://gbdev.io/pandocs/print.html

Steps to start a game using the EMS mapper, assuming code is running from RAM.

```text
Write $A5 to $1000
Write game’s first bank number to $2000
Write any value to $7000
Write $98 to $1000
Write $01 to $2000 (so that 32K games work)
Jump to $0100
```

--------------------------------

### Switching from Transmission to Ping Phase Example

Source: https://gbdev.io/pandocs/print.html

Demonstrates the sequence of events when switching from the transmission phase back to the ping phase, including the $FF indicator packet.

```text
Packet Byte| Received From  
DMG-07| Game Boy Reply| Meaning  
---|---|---|---
Byte 1| $81| $81| Game Boy sends its last transmission data ($81)  
Byte 2| $A5| $00| Data from Player 2 ($A5)  
Byte 3| $A5| $00| Data from Player 3 ($A5)  
Byte 4| $A5| $00| Data from Player 4 ($A5)  
| | |   
Byte 1| $81| $FF| Game Boy initiates ping restart (4×$FF)  
Byte 2| $A5| $FF|   
Byte 3| $A5| $FF|   
Byte 4| $A5| $FF|   
| | |   
Byte 1| $FF| $00| Start of switch to ping indicator from DMG-07 (4×$FF)  
Byte 2| $FF| $00|   
Byte 3| $FF| $00|   
Byte 4| $FF| $00| Final switch to ping indicator from DMG-07  
| | |   
Byte 1| $FE| $00| Now returned to ping phase, start of first Ping packet  
Byte 2| $01| $88|   
Byte 3| $01| $88|   
Byte 4| $F1| $00|   
```

--------------------------------

### Disable Rumble

Source: https://gbdev.io/pandocs/MBC5.html

Example of disabling the rumble motor.

```assembly
ld a, $00
ldh [rJOYP], a
```

--------------------------------

### CB-Prefix Instructions

Source: https://gbdev.io/pandocs/print.html

Indicates the start of a CB-prefixed instruction block.

```Assembly
| 7| 6| 5| 4| 3| 2| 1| 0  
---|---|---|---|---|---|---|---|
**Prefix (see block below)**|  1| 1| 0| 0| 1| 0| 1| 1
```
Tokens:
Raw