dZ80

dZ80 is a cool freeware application designed to disassemble code for the Zilog Z80 Processor. If you've got a raw binary file, this tool can break it down into understandable parts. It’s especially handy because it correctly disassembles all those tricky undocumented instructions that many other tools might skip over. This includes those weird instructions like 'LD r, RLC (IX+4)' and even supports Z180 instructions that fill some gaps in the EDxx opcode range.

How dZ80 Works

When you’re using dZ80 to disassemble a file, there are four important things you need to tell it:

1. Starting Point of Data

You need to know where the actual data begins in your file. For example, some files like .SNA files (which are snapshots from the Sinclair ZX Spectrum) have a 27-byte header before the main data starts. By default, dZ80 won’t skip any bytes, so you’ll need to use the command line option -h=[bytes to skip] to tell it how many bytes to skip.

2. Memory Space Start Address

You also have to specify where in the Z80's memory space your file starts. For .SNA files, this usually begins at address 16384 and goes up to 65535. By default, dZ80 thinks everything starts at address 0 unless you change it with -m=[memory base].

3. Disassembly Start Location

The next thing is deciding where in memory you want dZ80 to start disassembling from. The tool will usually kick off from whatever address you set with -m, or from 0 if you don’t change anything. You can adjust this starting point using -s=[start disassembly].

4. Disassembly End Location

Lastly, you'll want to define where the disassembly should stop. By default, it will continue until the end of your source file is reached. To set an end point manually, use -e=[end disassembly].

dZ80 automatically adjusts points i and ii for .SNA files—setting them at 27 and 16384 respectively—making life easier! There might be support for more file types in future updates too.

If you're ready to check out dZ80 or download it now, just click this link: dZ80 Download Page!