DEZ80

This repository holds the code for all of the challenges of the DEZ80 course.

Check out the README.md inside each level's subfolder for a preview of all of them.

Trying out the code

All of the code in this repository has been tested in WinAPE using the CPC 464 with ParaDOS preset.

Levels 1 and 2

• Copy the machine code that you want to test.
• Open the debugger window of WinApe.
• Paste the code in the memory position 0x4000 (use Ctrl+G or Right Click > Goto...).
• Change the value of the PC to the position where the code starts. By default this will be where you pasted the code in the previous step, but some programs store data at the beginning so their code will start at a higher position. The comments in each section (or a lot of 0s in the middle of the machine code) should make it clear if this is the case.
• Close the debugger window and the program will execute.

NOTE: Some of these machine code programs assume that executable instructions start at position 0x4000 and reference memory positions directly based on this assumption (e.g. to store data). This is for the sake of simplicity or complying with constraints for that specific challenge (e.g. use specific instruction).

Level 3

• Open the assembler window.
• Open the .asm file.
• Assemble and run (Assemble > Run or F9).

Links

• Course link (Dominando Ensamblador Z80)
• Z80 User Manual
• Z80 Instruction Set
• Amstrad CPC Firmware guide
• Amstrad CPC User Instructions (keycodes in page 334)

Notes

Time

CRTC generates an interruption every time it draws 52 rows of the screen and generates 300 interrupts/s. Therefore:

300 interrupts/s

6 interrupts/frame

300/6 = 50 frame/s

Video mode 1 (default)

Color encoding

Each byte encodes 4 pixels (2 bits per pixel). The byte is split into two nibbles and the same index within both nibbles corresponds to a single pixel.

	Index
Nibble 1	0123
Nibble 2	0123

The two bits of each pixel should be set according to the following table:

Red	Yellow	Cyan	Blue
1	1	0	0
1	0	1	0

See examples below for specific encoding examples.

Examples

	rrrr
Nibble 1	1111
Nibble 2	1111
Byte	0xFF

	rryy
Nibble 1	1111
Nibble 2	1100
Byte	0xFC

	rycb
Nibble 1	1100
Nibble 2	1010
Byte	0xCA