The chiposlo from tobiasvl

chiposlo's Introduction

Read my blog, where I write about my projects.

Latest blog posts

Running CHIP-8 on an HP 48 calculator (2020-10-13)
Guide to making a CHIP-8 emulator (2020-07-20)
Emulating the Space Invaders look and feel (2020-06-09)
An emulator UI (2020-05-31)
Choosing the wrong M6800 assembler (2020-04-29)

I'm a hobbyist game developer, and my games can be found on my itch.io page (as well as here on GitHub). I like making games in small, restrictive retro-esque game environments such as PICO-8, CHIP-8, bitsy, Game Boy, etc.

Games

Picolarium: A PICO-8 "demake" of the Nintendo DS game Polarium
Meteor Night: A short PICO-8 experience about watching shooting stars with a loved one
Mini Lights Out: A CHIP-8 version of the classic Mini Lights Out puzzle game
Patrick's Cyberpunk Challenge: A PICO-8 puzzle game
Patrick's Pocket Challenge: A Game Boy version of Patrick's Challenge
LaserTank for PICO-8: A PICO-8 version of the puzzle game LaserTank
PICO-@: A prototype for a roguelike in PICO-8
Soko All Stars: A prototype for a Sokoban-like puzzle game in LÖVE

I love retro computing, and have a few related projects:

LADX Disassembly: I'm a contributor to the The Legend of Zelda: Link's Awakening DX disassembly project
- Legenden om Zelda: Links oppvåkning: Norwegian translation of Link's Awakening
DRÖM: Lua/LÖVE-based emulator of the DREAM 6800 microcomputer
- CHIPOSLO: A modified version of the DREAM's CHIP-8 interpreter, written in M6800 assembly
Moon Invaders: Lua/LÖVE-based emulator of the Space Invaders Intel 8080 arcade cabinet
Optable: A website with opcode tables for various 8-bit CPUs
CHIP-8 research: A website/organization with information about CHIP-8.

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chiposlo's Issues

Incorporate suggestions from Peter Ferrie

tobiasvl/tobiasvl.github.io#1

Opcode Ex9E not working as expected

First of all: Thank you for your work on an improved CHIPOS version!

While testing it agains my DREAM6800 emulation, I came across an issue that is resulting from the modifications:

The Ex9E opcode is not working in the current CHIPOSLO version. The Problem originates in the reorganization of the skip opcode handling.

The relevant code:

SKFKEY: JSR     KEYINP      ; INTERROGATE KEYBOARD  <--- This sets the key in KEYCOD and A, A not same as PIR+1 anymore!!!
        TST     BADRED      ; KEY DOWN?
        BEQ     SKFK1
        LDAB    #$A1        ; WHAT INSTRN?
        CMPB    PIR+1       ; SKF VX#KEY   <--- This still works as it doesn't rely on A being content of PIR+1
        BEQ     SKIP2
        RTS                 ; NO KEY GO FETCH
SKFK1:  CMPA    #$9E.       ;  <--- But this now compares the pressed key against $9E, not the second opcode byte
        BEQ     SKFEQ
SKFNE:  CMPA    VX
        BNE     SKIP2
        RTS
LETVK:  ADDA    VX
        BRA     PUTVX
RANDV:  BSR     RANDOM      ; GET RANDOM BYTE
        ANDA    PIR+1
        BRA     PUTVX

The original code in comparison does explicitly use PIR+1:

SKFK1:  LDAB  	#$9E
        CMPB  	PIR+1       ; WHAT INSTRN?
        BEQ     SKFEQ
        BRA     SKFNE

I might try to fix it myself and would put out a PR if I do, but I'm not sure if and when I would manage to do so.

tobiasvl / chiposlo Goto Github PK

chiposlo's Introduction

chiposlo's People

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chiposlo's Issues

Incorporate suggestions from Peter Ferrie

Opcode Ex9E not working as expected

VX and VY need to be moved back

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