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a9ed8da0b2
The previous approach of maintaining R> and W> pointers was conceptually simple, but made INT handler code actually quite complex. Now, we maintain indexes instead. It's much easier to perform bounds checks and to compare for equality, something we have to do quick in the INT handler.
15 lines
443 B
Plaintext
15 lines
443 B
Plaintext
: (key)
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( inc then fetch )
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[ ACIAR> LITN ] C@ 1+ [ ACIA_BUFSZ 1- LITN ] AND
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( As long as R> == W>-1, it means that buffer is empty )
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BEGIN DUP [ ACIAW> LITN ] C@ = NOT UNTIL
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DUP [ ACIA( LITN ] @ + C@ ( ridx c )
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SWAP [ ACIAR> LITN ] C! ( c )
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;
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: (emit)
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( As long at CTL bit 1 is low, we are transmitting. wait )
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BEGIN [ ACIA_CTL LITN ] PC@ 0x02 AND UNTIL
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( The way is clear, go! )
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[ ACIA_IO LITN ] PC!
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;
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