At the end of the rainbow
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The ins and outs of writing a ZX Spectrum emulator using Lua 5.3 using bitwise operators, dynamic code generation and string.unpack.
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At the end of the rainbow
- 1. Ignacio Burgueño Lua Workshop 2015 Stockholm, Sweden At the end of the rainbow
- 2. About Me Ignacio Burgueño Developer at inConcert @iburgueno https://github.com/ignacio
- 3. What will be talking about? ● Writing a ZX Spectrum emulator in Lua 5.3 ● Fun with Bitwise operators
- 4. A bit of history
- 13. What is needed? ● Replace hardware parts with software ● Which parts?
- 15. Architecture "ZX Spectrum block diagram" taken from the book “The ZX Spectrum ULA” by Chris Smith
- 16. Memory
- 17. CPU "Z80 arch" by Appaloosa - Own work. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/File:Z80_arch.svg#/media/File:Z80_arch.svg Instruction Register Instruction Decoder Control Logic I R 1+_ 1+_ MUXMUX W ZW' Z' BB' CC' DD' EE' H LH' L' IX IY PC SP TEMP ACU A A' F F' + BUFFERSBUFFERSBUFFERS ALU Internal Data Bus 8 Bit Address Bus 16 Bit Control Bus Control Section Z80 Architecture
- 18. CPU
- 19. CPU – Instruction Set ● 8-bit arithmetic and logic operations ● 16-bit arithmetic ● 8-bit load ● 16-bit load ● Bit set, reset, and test ● Call, return, and restart ● Exchange, block transfer, and search ● General purpose arithmetic and CPU control ● Input and output ● Jump ● Rotate and shift LD A,42 0x3e 0x2a
- 20. CPU – Fetch/Execute Cycle
- 21. CPU – Fetch/Execute Cycle
- 22. CPU – Fetch/Execute Cycle
- 23. CPU – Fetch/Execute Cycle
- 24. CPU - Opcodes
- 25. CPU – Instruction families ● Same operation is applied to different registers ● One instruction for each combination ● Avoid writing the same function over and over ● Generate them using a template
- 26. CPU – Instruction families
- 27. CPU – Instruction families
- 28. CPU – Instruction families
- 29. See what's going on
- 30. Drawing to the Screen
- 31. Drawing to the Screen
- 32. Drawing to the Screen
- 33. Drawing to the Screen
- 34. Drawing to the Screen luasdl2 https://github.com/Tangent128/luasdl2 More information on the subject: How "oldschool" graphics worked video series
- 35. Getting software in it (aka, how do I load games on this?)
- 36. Parsing Binary data Offset (bytes) Size Description 0 1 byte I 1 8 words HL', DE', BC', AF' 9 10 words HL, DE, BC, IY, IX 19 1 byte Interrupt 20 1 byte R 21 4 words AF, SP 25 1 byte Interruption Mode 26 1 byte Border Color 27 49152 bytes RAM dump 16384 .. 65535 Total: 49179 bytes File Formats - SNA
- 37. File Formats - SNA ● Parsing binary formats ● Don't want to split strings ● Enter string.unpack
- 38. File Formats - SNA ● Cumbersome to read ● What value ends up where? ● Extend the unpack format string
- 39. File Formats - SNA
- 40. File Formats - SNA
- 41. Testing ● Run little code snippets ● Make sure registers have the correct values ● Correct memory locations are read and written at the right times
- 42. Testing ● Run little code snippets ● Make sure registers have the correct values ● Correct memory locations are read and written at the right times
- 43. Demo
- 44. Where to get it? https://github.com/ignacio/luagleck Where do I get software to try? http://www.worldofspectrum.org/archive.html
- 45. Thank you! Any questions? Ignacio Burgueño - @iburgueno