explain a number of KERNAL coincidental similarities.

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Paul Gardner-Stephen committed 2019-05-07 10:20:35 +09:30
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Do something with $DD00 and compare it with some value.
$DD00 is one of the CIA ports, so checking the value of inputs
on this port is something rather expected and common.
Also, this sequence doesn't even contain a whole instruction.
Not copyrightable.
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Do something with $DD00 and return from sub-routine.
Only one whole instruction. Also $DD00 is a CIA IO port, and
so it gets used quite a lot, so is no surprise to see it appearing.
Not copyrightable.
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do something with $DD00, then RTS, then read $DD00
Again, $DD00 is a CIA IO register, and so there are a number
of routines that are required that simply check or modify the
contents of this register in order to implement the IEC serial
protocol. Thus it is totally unsurprising to find routines that
start by reading $DD00 and then processing it in some way.
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Instruction fragment + CLC + RTS
C flag is used to indicate success/failure of many KERNAL routines.
Thus finding CLC before an RTS is not at all surprising, and the
obvious way to indicate success in a routine.
Not copyrightable.
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Return from subroutine, then read $DD00 , and do something with it.
Again, $DD00 is a CIA IO register, and so there are a number
of routines that are required that simply check or modify the
contents of this register in order to implement the IEC serial
protocol. Thus it is totally unsurprising to find routines that
start by reading $DD00 and then processing it in some way.
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Return from subroutine, then read $DD00 , and do something with it.
Again, $DD00 is a CIA IO register, and so there are a number
of routines that are required that simply check or modify the
contents of this register in order to implement the IEC serial
protocol. Thus it is totally unsurprising to find routines that
start by reading $DD00 and then processing it in some way.
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Part of JSR $FFD2 / INX
Essentially part of a loop to print some characters.
No creativity. Only a single whole instruction.
Not copyrightable.
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do something with $DD00, then RTS, then read $DD00
Again, $DD00 is a CIA IO register, and so there are a number
of routines that are required that simply check or modify the
contents of this register in order to implement the IEC serial
protocol. Thus it is totally unsurprising to find routines that
start by reading $DD00 and then processing it in some way.
+7
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@@ -0,0 +1,7 @@
do something with $DD00, then RTS, then read $DD00
Again, $DD00 is a CIA IO register, and so there are a number
of routines that are required that simply check or modify the
contents of this register in order to implement the IEC serial
protocol. Thus it is totally unsurprising to find routines that
start by reading $DD00 and then processing it in some way.