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

This commit is contained in:
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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@ -0,0 +1,81 @@
incdir "tests"
include "dsp_base.inc"
; Tests the behavior of SI, SRS, and LRS when CR is changed
; Register that is writable but with contents that doesn't matter (COEF_A1_0)
TEST_REG: equ 0xFFA0 ; 0xFF00 (not writable)
; This is separate because SRS and SI currently require value 0..7f or ff80..ffff,
; though the actual behavior doesn't match that
TEST_ADDR: equ 0xFFA0 ; 0x0000
; Memory addresses
TEST_MEM: equ 0x00A0 ; 0x0000
TEST_MEM_2: equ 0x01A0 ; 0x0100
LRI $AC0.L, #0xf00f
SR @TEST_REG, $AC0.L
SR @TEST_MEM, $AC0.L
SR @TEST_MEM_2, $AC0.L
CALL send_regs
; Observed: writes to TEST_REG
SI @TEST_ADDR, #0xf11f
CALL send_regs
LRI $AC0.L, #0xf22f
; Observed: writes to TEST_REG
SRS @TEST_ADDR, $AC0.L
CALL send_regs
LRI $CR, #0x0000
; Observed: still writes to TEST_REG
SI @TEST_ADDR, #0xf33f
CALL send_regs
LRI $AC0.L, #0xf44f
; Observed: writes to TEST_MEM
SRS @TEST_ADDR, $AC0.L
CALL send_regs
LRI $CR, #0x0001
; Observed: still writes to TEST_REG
SI @TEST_ADDR, #0xf55f
CALL send_regs
LRI $AC0.L, #0xf66f
; Observed: writes to TEST_MEM_2
SRS @TEST_ADDR, $AC0.L
CALL send_regs
; At this point, TEST_REG should be f55f, TEST_MEM should be f44f,
; and TEST_MEM_2 should be f66f. Test the behavior of LRS.
; Changes to prod.l are for display only.
LRI $CR, #0x00ff
LRI $prod.l, #0xf55f
LRS $AC0.L, @TEST_ADDR
CALL send_regs
LRI $CR, #0x0000
LRI $prod.l, #0xf44f
LRS $AC0.L, @TEST_ADDR
CALL send_regs
LRI $CR, #0x0001
LRI $prod.l, #0xf66f
LRS $AC0.L, @TEST_ADDR
CALL send_regs
; We're done, DO NOT DELETE THIS LINE
JMP end_of_test
send_regs:
; For display purposes only
LRI $prod.m1, #TEST_REG
LRI $prod.h, #TEST_MEM
LRI $prod.m2, #TEST_MEM_2
; Actual registers
LR $AC1.L, @TEST_REG
LR $AC0.M, @TEST_MEM
LR $AC1.M, @TEST_MEM_2
CALL send_back
RET

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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} \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. 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} \end{DSPOpcodeFormat}
\begin{DSPOpcodeDescription} \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. Perform an additional operation depending on destination register.
\end{DSPOpcodeDescription} \end{DSPOpcodeDescription}
\begin{DSPOpcodeOperation} \begin{DSPOpcodeOperation}
$(0x18+D) = MEM[M] $(0x18+D) = MEM[($cr << 8) | M]
$pc++ $pc++
\end{DSPOpcodeOperation} \end{DSPOpcodeOperation}
@ -3843,14 +3843,18 @@ A ``-'' indicates that the flag retains its previous value, a ``0'' indicates th
\end{DSPOpcodeFormat} \end{DSPOpcodeFormat}
\begin{DSPOpcodeDescription} \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} \end{DSPOpcodeDescription}
\begin{DSPOpcodeOperation} \begin{DSPOpcodeOperation}
MEM[M] = I MEM[0xFF00 | M] = I
$pc += 2 $pc += 2
\end{DSPOpcodeOperation} \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 \DSPOpcodeFlagsUnchanged
\end{DSPOpcode} \end{DSPOpcode}
@ -3979,12 +3983,12 @@ A ``-'' indicates that the flag retains its previous value, a ``0'' indicates th
\end{DSPOpcodeFormat} \end{DSPOpcodeFormat}
\begin{DSPOpcodeDescription} \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. Perform an additional operation depending on destination register.
\end{DSPOpcodeDescription} \end{DSPOpcodeDescription}
\begin{DSPOpcodeOperation} \begin{DSPOpcodeOperation}
MEM[M] = $(0x18+S) MEM[($cr << 8) | M] = $(0x18+S)
$pc++ $pc++
\end{DSPOpcodeOperation} \end{DSPOpcodeOperation}