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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 $8800
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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 #$0b
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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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