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README.md

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+## Z80 CPU Emulator
+
+This is a Zilog Z80 CPU emulator, written in Python. 
+It runs a 1978 Microsoft Basic 4.7 ROM taken from [Grant Searle's Z80 SBC project](http://searle.hostei.com/grant/z80/SimpleZ80.html)
+
+### Why?
+Just for fun. I like the Z80 CPU - it was in many devices I played with as a
+kid. 
+
+### Is it useful?
+No. It runs really slowly, and is a completely non-optimal software design for
+an emulator, but (in my opinion) the code is readable. If you want a CPU emulator, 
+probably don't use Python. That said, an optimised python coded emulator could run 
+a lot faster than this :-)
+
+### Running
+BASIC:
+```
+cd src
+python z80sbc.py
+```
+Unit tests:
+```
+cd src
+PYTHONPATH=`pwd`:$PYTHONPATH python ../tests/test_z80.py
+PYTHONPATH=`pwd`:$PYTHONPATH python ../tests/test_registers.py
+```
+
+Fuse tests:
+```
+cd src
+PYTHONPATH=`pwd`:$PYTHONPATH python ../fuse_tests/tests.py
+```
+
+### Missing and todo
+- Most undocumented opcodes
+- Undocumented flags for `CPI` and `CPIR`.
+
+### Credits
+
+[Grant Searle's Z80 SBC project](http://searle.hostei.com/grant/z80/SimpleZ80.html)
+
+[FUSE - Free Unix Spectrum Emulator](http://fuse-emulator.sourceforge.net/) for the instruction set tests
+
+### License
+Public domain; do what you like.