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docs/DSP: Document behavior of LRS/SRS/SI with CR

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Pokechu22
2021-08-14 17:36:55 -07:00
parent 8fa649e1d6
commit 408623b6e9
2 changed files with 92 additions and 7 deletions
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18
docs/DSP/GameCube_DSP_Users_Manual/GameCube_DSP_Users_Manual.tex
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@ -534,7 +534,7 @@ If the value is not zero, then the PC is modified by the value from call stack \
\section{Config register}
Its purpose is unknown at this time. It is written with \Value{0x00FF} and \Value{0x0004} values.
Serves as a base offset for \Opcode{SRS} and \Opcode{LRS}. Zelda uCode writes it with \Value{0x0004}, but otherwise it is usually \Value{0x00FF}.
This is an 8-bit register. Writes to the upper 8 bits are ignored and those bits always read back as 0.
@ -2558,12 +2558,12 @@ A ``-'' indicates that the flag retains its previous value, a ``0'' indicates th
\end{DSPOpcodeFormat}
\begin{DSPOpcodeDescription}
\item Move value from data memory pointed by address \Address{M} (8-bit sign-extended) to register \Register{\$(0x18+D)}.
\item Move value from data memory pointed by address \Address{(\$cr << 8) | M} to register \Register{\$(0x18+D)}.
Perform an additional operation depending on destination register.
\end{DSPOpcodeDescription}
\begin{DSPOpcodeOperation}
$(0x18+D) = MEM[M]
$(0x18+D) = MEM[($cr << 8) | M]
$pc++
\end{DSPOpcodeOperation}
@ -3843,14 +3843,18 @@ A ``-'' indicates that the flag retains its previous value, a ``0'' indicates th
\end{DSPOpcodeFormat}
\begin{DSPOpcodeDescription}
\item Store 16-bit immediate value \Value{I} to a memory location pointed by address \Address{M} (\Address{M} is an 8-bit sign-extended value).
\item Store 16-bit immediate value \Value{I} to a memory location pointed by address \Address{0xFF00 | M}.
\end{DSPOpcodeDescription}
\begin{DSPOpcodeOperation}
MEM[M] = I
MEM[0xFF00 | M] = I
$pc += 2
\end{DSPOpcodeOperation}
\begin{DSPOpcodeNote}
\item Unlike \Opcode{LRS} and \Opcode{SRS}, \Opcode{SI} does not use \Register{\$cr} to decide the base address and instead always uses \Address{0xFF00}.
\end{DSPOpcodeNote}
\DSPOpcodeFlagsUnchanged
\end{DSPOpcode}
@ -3979,12 +3983,12 @@ A ``-'' indicates that the flag retains its previous value, a ``0'' indicates th
\end{DSPOpcodeFormat}
\begin{DSPOpcodeDescription}
\item Store value from register \Register{\$(0x18+S)} to a memory pointed by address \Address{M} (8-bit sign-extended).
\item Store value from register \Register{\$(0x18+S)} to a memory pointed by address \Address{(\$cr << 8) | M}.
Perform an additional operation depending on destination register.
\end{DSPOpcodeDescription}
\begin{DSPOpcodeOperation}
MEM[M] = $(0x18+S)
MEM[($cr << 8) | M] = $(0x18+S)
$pc++
\end{DSPOpcodeOperation}