Seth Morabito
795ccfde5d
Bug Fixes: - Fixed several bugs in the CPU that caused processor status flags to be set incorrectly. Instructions affected were: STA, STX, STY, CMP, CPX, CPY, BIT. - Made some internal-use-only methods on the CPU class private. - Fixed incorrect disassembly of (Indirect,X) and (Indirect),Y instructions. Although this didn't affect behavior, it certainly caused me some confusion in debugging. - Added missing "BCS" instruction to instruction table. Enhancements: - Now includes a full version of Lee Davison's Enhanced 6502 BASIC bundled as source code and a ROM image. Get that REAL COMPUTER EXPERIENCE!(tm) - If a file named "rom.bin" exists in the same directory where the simulator is executed, it will be loaded at addresses $d000-$ffff. - Gave the CPU an idle loop to make simulated timing a little more realistic (but this is still an area needing major improvement) - Changed the CPU's toString() method to give better debugging output. - Added a small typeahead buffer to the Console. - Better exception messaging. Misc: - Bumped version to 0.5, updated README.
37 lines
1005 B
NASM
37 lines
1005 B
NASM
;;
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;; Read input from the keyboard, and echo to console.
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;;
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.alias iobase $c000
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.alias iostatus [iobase + 1]
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.alias iocmd [iobase + 2]
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.alias ioctrl [iobase + 3]
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.org $0300
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start: cli
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lda #$09
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sta iocmd ; Set command status
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lda #$1a
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sta ioctrl ; 0 stop bits, 8 bit word, 2400 baud
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;; Load a character from the keyboard and store it into
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;; the accumulator
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getkey: lda iostatus ; Read the ACIA status
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and #$08 ; Is the rx register empty?
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beq getkey ; Yes, wait for it to fill
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lda iobase ; Otherwise, read into accumulator
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;; Write the current char in the accumulator to the console
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write: pha ; Save accumulator
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writel: lda iostatus ; Read the ACIA status
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and #$10 ; Is the tx register empty?
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beq writel ; No, wait for it to empty
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pla ; Otherwise, load saved accumulator
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sta iobase ; and write to output.
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jmp getkey ; Repeat
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