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Improve the instruction documentation (#1561)

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Sylvie
2024-12-02 15:41:57 -05:00
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parent d5f39c8dce
commit 6982c8a116
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man/gbz80.7
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@@ -9,7 +9,7 @@
.Sh DESCRIPTION .Sh DESCRIPTION
This is the list of opcodes supported by This is the list of opcodes supported by
.Xr rgbasm 1 , .Xr rgbasm 1 ,
including a short description, the number of bytes needed to encode them and the number of CPU cycles at 1MHz (or 2MHz in GBC dual speed mode) needed to complete them. including a short description, the number of bytes needed to encode them and the number of CPU cycles at 1MHz (or 2MHz in GBC double speed mode) needed to complete them.
.Pp .Pp
Note: All arithmetic and logic instructions that use register Note: All arithmetic and logic instructions that use register
.Sy A .Sy A
@@ -43,23 +43,36 @@ Any of the 8-bit registers
Any of the general-purpose 16-bit registers Any of the general-purpose 16-bit registers
.Pq Sy BC , DE , HL . .Pq Sy BC , DE , HL .
.It Ar n8 .It Ar n8
8-bit integer constant. 8-bit integer constant
.Po signed or unsigned,
.Sy -128
to
.Sy 255
.Pc .
.It Ar n16 .It Ar n16
16-bit integer constant. 16-bit integer constant
.Po signed or unsigned,
.Sy -32768
to
.Sy 65535
.Pc .
.It Ar e8 .It Ar e8
8-bit offset 8-bit signed offset
.Po Sy -128 .Po Sy -128
to to
.Sy 127 .Sy 127
.Pc . .Pc .
.It Ar u3 .It Ar u3
3-bit unsigned integer constant 3-bit unsigned bit index
.Po Sy 0 .Po Sy 0
to to
.Sy 7 .Sy 7 ,
with
.Sy 0
as the least significant bit
.Pc . .Pc .
.It Ar cc .It Ar cc
Condition codes: A condition code:
.Bl -tag -width Ds -compact .Bl -tag -width Ds -compact
.It Sy Z .It Sy Z
Execute if Z is set. Execute if Z is set.
@@ -71,9 +84,9 @@ Execute if C is set.
Execute if C is not set. Execute if C is not set.
.El .El
.It Ar vec .It Ar vec
One of the An
.Sy RST .Sy RST
vectors vector
.Po Ad 0x00 , 0x08 , 0x10 , 0x18 , 0x20 , 0x28 , 0x30 , .Po Ad 0x00 , 0x08 , 0x10 , 0x18 , 0x20 , 0x28 , 0x30 ,
and and
.Ad 0x38 Pc . .Ad 0x38 Pc .
@@ -363,7 +376,9 @@ Set if overflow from bit 3.
Set if overflow from bit 7. Set if overflow from bit 7.
.El .El
.Ss AND A,r8 .Ss AND A,r8
Bitwise AND between the value in Set
.Sy A
to the bitwise AND between the value in
.Ar r8 .Ar r8
and and
.Sy A . .Sy A .
@@ -384,7 +399,9 @@ Set if result is 0.
0 0
.El .El
.Ss AND A,[HL] .Ss AND A,[HL]
Bitwise AND between the byte pointed to by Set
.Sy A
to the bitwise AND between the byte pointed to by
.Sy HL .Sy HL
and and
.Sy A . .Sy A .
@@ -396,7 +413,9 @@ Bytes: 1
Flags: See Flags: See
.Sx AND A,r8 .Sx AND A,r8
.Ss AND A,n8 .Ss AND A,n8
Bitwise AND between the value in Set
.Sy A
to the bitwise AND between the value
.Ar n8 .Ar n8
and and
.Sy A . .Sy A .
@@ -443,6 +462,7 @@ Flags: See
.Ss CALL n16 .Ss CALL n16
Call address Call address
.Ar n16 . .Ar n16 .
.Pp
This pushes the address of the instruction after the This pushes the address of the instruction after the
.Sy CALL .Sy CALL
on the stack, such that on the stack, such that
@@ -484,12 +504,16 @@ Flags:
Inverted. Inverted.
.El .El
.Ss CP A,r8 .Ss CP A,r8
Subtract the value in ComPare the value in
.Sy A
with the value in
.Ar r8 .
.Pp
This subtracts the value in
.Ar r8 .Ar r8
from from
.Sy A .Sy A
and set flags accordingly, but don't store the result. and sets flags accordingly, but discards the result.
This is useful for ComParing values.
.Pp .Pp
Cycles: 1 Cycles: 1
.Pp .Pp
@@ -510,11 +534,16 @@ Set if borrow (i.e. if
.Sy A ) . .Sy A ) .
.El .El
.Ss CP A,[HL] .Ss CP A,[HL]
Subtract the byte pointed to by ComPare the value in
.Sy A
with the byte pointed to by
.Sy HL .
.Pp
This subtracts the byte pointed to by
.Sy HL .Sy HL
from from
.Sy A .Sy A
and set flags accordingly, but don't store the result. and sets flags accordingly, but discards the result.
.Pp .Pp
Cycles: 2 Cycles: 2
.Pp .Pp
@@ -523,11 +552,16 @@ Bytes: 1
Flags: See Flags: See
.Sx CP A,r8 .Sx CP A,r8
.Ss CP A,n8 .Ss CP A,n8
Subtract the value ComPare the value in
.Sy A
with the value
.Ar n8 .
.Pp
This subtracts the value
.Ar n8 .Ar n8
from from
.Sy A .Sy A
and set flags accordingly, but don't store the result. and sets flags accordingly, but discards the result.
.Pp .Pp
Cycles: 2 Cycles: 2
.Pp .Pp
@@ -540,7 +574,8 @@ ComPLement accumulator
.Po Sy A .Po Sy A
= =
.Sy ~A .Sy ~A
.Pc . .Pc ;
also called bitwise NOT.
.Pp .Pp
Cycles: 1 Cycles: 1
.Pp .Pp
@@ -560,7 +595,8 @@ Designed to be used after performing an arithmetic instruction
.Pq Sy ADD , ADC , SUB , SBC .Pq Sy ADD , ADC , SUB , SBC
whose inputs were in Binary-Coded Decimal (BCD), adjusting the result to likewise be in BCD. whose inputs were in Binary-Coded Decimal (BCD), adjusting the result to likewise be in BCD.
.Pp .Pp
The exact behavior of this instruction is as follows: The exact behavior of this instruction depends on the state of the subtract flag
.Sy N :
.Bl -tag -width Ds -offset indent .Bl -tag -width Ds -offset indent
.It If the subtract flag Sy N No is set: .It If the subtract flag Sy N No is set:
.Bl -enum -compact .Bl -enum -compact
@@ -629,7 +665,7 @@ Set if result is 0.
Set or reset depending on the operation. Set or reset depending on the operation.
.El .El
.Ss DEC r8 .Ss DEC r8
Decrement value in register Decrement the value in register
.Ar r8 .Ar r8
by 1. by 1.
.Pp .Pp
@@ -658,7 +694,7 @@ Bytes: 1
Flags: See Flags: See
.Sx DEC r8 .Sx DEC r8
.Ss DEC r16 .Ss DEC r16
Decrement value in register Decrement the value in register
.Ar r16 .Ar r16
by 1. by 1.
.Pp .Pp
@@ -668,7 +704,7 @@ Bytes: 1
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss DEC SP .Ss DEC SP
Decrement value in register Decrement the value in register
.Sy SP .Sy SP
by 1. by 1.
.Pp .Pp
@@ -691,6 +727,7 @@ Flags: None affected.
Enable Interrupts by setting the Enable Interrupts by setting the
.Sy IME .Sy IME
flag. flag.
.Pp
The flag is only set The flag is only set
.Em after .Em after
the instruction following the instruction following
@@ -703,28 +740,26 @@ Bytes: 1
Flags: None affected. Flags: None affected.
.Ss HALT .Ss HALT
Enter CPU low-power consumption mode until an interrupt occurs. Enter CPU low-power consumption mode until an interrupt occurs.
.Pp
The exact behavior of this instruction depends on the state of the The exact behavior of this instruction depends on the state of the
.Sy IME .Sy IME
flag. flag, and whether interrupts are pending (i.e. whether
.Bl -tag -width Ds .Ql [IE] & [IF]
.It Sy IME No set is non-zero):
.Bl -tag -width Ds -offset indent
.It If the Sy IME No flag is set:
The CPU enters low-power mode until The CPU enters low-power mode until
.Em after .Em after
an interrupt is about to be serviced. an interrupt is about to be serviced.
The handler is executed normally, and the CPU resumes execution after the The handler is executed normally, and the CPU resumes execution after the
.Ic HALT .Ic HALT
when that returns. when that returns.
.It Sy IME No not set .It If the Sy IME No flag is not set, and no interrupts are pending:
The behavior depends on whether an interrupt is pending (i.e.\&
.Ql [IE] & [IF]
is non-zero).
.Bl -tag -width Ds
.It None pending
As soon as an interrupt becomes pending, the CPU resumes execution. As soon as an interrupt becomes pending, the CPU resumes execution.
This is like the above, except that the handler is This is like the above, except that the handler is
.Em not .Em not
called. called.
.It Some pending .It If the Sy IME No flag is not set, and some interrupt is pending:
The CPU continues execution after the The CPU continues execution after the
.Ic HALT , .Ic HALT ,
but the byte after it is read twice in a row but the byte after it is read twice in a row
@@ -733,7 +768,6 @@ but the byte after it is read twice in a row
is not incremented, due to a hardware bug is not incremented, due to a hardware bug
.Pc . .Pc .
.El .El
.El
.Pp .Pp
Cycles: - Cycles: -
.Pp .Pp
@@ -741,7 +775,7 @@ Bytes: 1
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss INC r8 .Ss INC r8
Increment value in register Increment the value in register
.Ar r8 .Ar r8
by 1. by 1.
.Pp .Pp
@@ -770,7 +804,7 @@ Bytes: 1
Flags: See Flags: See
.Sx INC r8 .Sx INC r8
.Ss INC r16 .Ss INC r16
Increment value in register Increment the value in register
.Ar r16 .Ar r16
by 1. by 1.
.Pp .Pp
@@ -780,7 +814,7 @@ Bytes: 1
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss INC SP .Ss INC SP
Increment value in register Increment the value in register
.Sy SP .Sy SP
by 1. by 1.
.Pp .Pp
@@ -792,7 +826,7 @@ Flags: None affected.
.Ss JP n16 .Ss JP n16
Jump to address Jump to address
.Ar n16 ; .Ar n16 ;
effectively, store effectively, copy
.Ar n16 .Ar n16
into into
.Sy PC . .Sy PC .
@@ -817,10 +851,11 @@ Flags: None affected.
.Ss JP HL .Ss JP HL
Jump to address in Jump to address in
.Sy HL ; .Sy HL ;
effectively, load effectively, copy
.Sy PC the value in register
with value in register .Sy HL
.Sy HL . into
.Sy PC .
.Pp .Pp
Cycles: 1 Cycles: 1
.Pp .Pp
@@ -830,6 +865,7 @@ Flags: None affected.
.Ss JR n16 .Ss JR n16
Relative Jump to address Relative Jump to address
.Ar n16 . .Ar n16 .
.Pp
The address is encoded as a signed 8-bit offset from the address immediately following the The address is encoded as a signed 8-bit offset from the address immediately following the
.Ic JR .Ic JR
instruction, so the target address instruction, so the target address
@@ -864,7 +900,16 @@ Bytes: 2
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD r8,r8 .Ss LD r8,r8
Load (copy) value in register on the right into register on the left. Copy (aka Load) the value in register on the right into the register on the left.
.Pp
Storing a register into itself is a no-op; however, some Game Boy emulators interpret
.Sy LD B,B
as a breakpoint, or
.Sy LD D,D
as a debug message
.Po such as
.Lk https://bgb.bircd.org/manual.html#expressions BGB
.Pc .
.Pp .Pp
Cycles: 1 Cycles: 1
.Pp .Pp
@@ -872,7 +917,7 @@ Bytes: 1
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD r8,n8 .Ss LD r8,n8
Load value Copy the value
.Ar n8 .Ar n8
into register into register
.Ar r8 . .Ar r8 .
@@ -883,7 +928,7 @@ Bytes: 2
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD r16,n16 .Ss LD r16,n16
Load value Copy the value
.Ar n16 .Ar n16
into register into register
.Ar r16 . .Ar r16 .
@@ -894,9 +939,9 @@ Bytes: 3
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD [HL],r8 .Ss LD [HL],r8
Store value in register Copy the value in register
.Ar r8 .Ar r8
into the byte pointed to by register into the byte pointed to by
.Sy HL . .Sy HL .
.Pp .Pp
Cycles: 2 Cycles: 2
@@ -905,9 +950,9 @@ Bytes: 1
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD [HL],n8 .Ss LD [HL],n8
Store value Copy the value
.Ar n8 .Ar n8
into the byte pointed to by register into the byte pointed to by
.Sy HL . .Sy HL .
.Pp .Pp
Cycles: 3 Cycles: 3
@@ -916,10 +961,10 @@ Bytes: 2
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD r8,[HL] .Ss LD r8,[HL]
Load value into register Copy the value pointed to by
.Ar r8 .Sy HL
from the byte pointed to by register into register
.Sy HL . .Ar r8 .
.Pp .Pp
Cycles: 2 Cycles: 2
.Pp .Pp
@@ -927,9 +972,9 @@ Bytes: 1
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD [r16],A .Ss LD [r16],A
Store value in register Copy the value in register
.Sy A .Sy A
into the byte pointed to by register into the byte pointed to by
.Ar r16 . .Ar r16 .
.Pp .Pp
Cycles: 2 Cycles: 2
@@ -938,7 +983,7 @@ Bytes: 1
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD [n16],A .Ss LD [n16],A
Store value in register Copy the value in register
.Sy A .Sy A
into the byte at address into the byte at address
.Ar n16 . .Ar n16 .
@@ -949,7 +994,7 @@ Bytes: 3
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LDH [n16],A .Ss LDH [n16],A
Store value in register Copy the value in register
.Sy A .Sy A
into the byte at address into the byte at address
.Ar n16 , .Ar n16 ,
@@ -969,7 +1014,7 @@ This is sometimes written as
or or
.Ql LD [$FF00+n8],A . .Ql LD [$FF00+n8],A .
.Ss LDH [C],A .Ss LDH [C],A
Store value in register Copy the value in register
.Sy A .Sy A
into the byte at address into the byte at address
.Ad $FF00+C . .Ad $FF00+C .
@@ -985,10 +1030,10 @@ This is sometimes written as
or or
.Ql LD [$FF00+C],A . .Ql LD [$FF00+C],A .
.Ss LD A,[r16] .Ss LD A,[r16]
Load value in register Copy the byte pointed to by
.Sy A .Ar r16
from the byte pointed to by register into register
.Ar r16 . .Sy A .
.Pp .Pp
Cycles: 2 Cycles: 2
.Pp .Pp
@@ -996,10 +1041,10 @@ Bytes: 1
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD A,[n16] .Ss LD A,[n16]
Load value in register Copy the byte at address
.Sy A .Ar n16
from the byte at address into register
.Ar n16 . .Sy A .
.Pp .Pp
Cycles: 4 Cycles: 4
.Pp .Pp
@@ -1007,10 +1052,10 @@ Bytes: 3
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LDH A,[n16] .Ss LDH A,[n16]
Load value in register Copy the byte at address
.Sy A .Ar n16
from the byte at address into register
.Ar n16 , .Sy A ,
provided the address is between provided the address is between
.Ad $FF00 .Ad $FF00
and and
@@ -1027,10 +1072,10 @@ This is sometimes written as
or or
.Ql LD A,[$FF00+n8] . .Ql LD A,[$FF00+n8] .
.Ss LDH A,[C] .Ss LDH A,[C]
Load value in register Copy the byte at address
.Sy A .Ad $FF00+c
from the byte at address into register
.Ad $FF00+c . .Sy A .
.Pp .Pp
Cycles: 2 Cycles: 2
.Pp .Pp
@@ -1043,7 +1088,7 @@ This is sometimes written as
or or
.Ql LD A,[$FF00+C] . .Ql LD A,[$FF00+C] .
.Ss LD [HLI],A .Ss LD [HLI],A
Store value in register Copy the value in register
.Sy A .Sy A
into the byte pointed by into the byte pointed by
.Sy HL .Sy HL
@@ -1062,7 +1107,7 @@ This is sometimes written as
or or
.Ql LDI [HL],A . .Ql LDI [HL],A .
.Ss LD [HLD],A .Ss LD [HLD],A
Store value in register Copy the value in register
.Sy A .Sy A
into the byte pointed by into the byte pointed by
.Sy HL .Sy HL
@@ -1081,10 +1126,10 @@ This is sometimes written as
or or
.Ql LDD [HL],A . .Ql LDD [HL],A .
.Ss LD A,[HLD] .Ss LD A,[HLD]
Load value into register Copy the byte pointed to by
.Sy A
from the byte pointed by
.Sy HL .Sy HL
into register
.Sy A ,
and decrement and decrement
.Sy HL .Sy HL
afterwards. afterwards.
@@ -1100,10 +1145,10 @@ This is sometimes written as
or or
.Ql LDD A,[HL] . .Ql LDD A,[HL] .
.Ss LD A,[HLI] .Ss LD A,[HLI]
Load value into register Copy the byte pointed to by
.Sy A
from the byte pointed by
.Sy HL .Sy HL
into register
.Sy A ,
and increment and increment
.Sy HL .Sy HL
afterwards. afterwards.
@@ -1119,7 +1164,7 @@ This is sometimes written as
or or
.Ql LDI A,[HL] . .Ql LDI A,[HL] .
.Ss LD SP,n16 .Ss LD SP,n16
Load value Copy the value
.Ar n16 .Ar n16
into register into register
.Sy SP . .Sy SP .
@@ -1130,7 +1175,7 @@ Bytes: 3
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss LD [n16],SP .Ss LD [n16],SP
Store Copy
.Sy SP .Sy SP
& &
.Ad $FF .Ad $FF
@@ -1153,7 +1198,7 @@ Add the signed value
.Ar e8 .Ar e8
to to
.Sy SP .Sy SP
and store the result in and copy the result in
.Sy HL . .Sy HL .
.Pp .Pp
Cycles: 3 Cycles: 3
@@ -1172,7 +1217,7 @@ Set if overflow from bit 3.
Set if overflow from bit 7. Set if overflow from bit 7.
.El .El
.Ss LD SP,HL .Ss LD SP,HL
Load register Copy register
.Sy HL .Sy HL
into register into register
.Sy SP . .Sy SP .
@@ -1191,9 +1236,9 @@ Bytes: 1
.Pp .Pp
Flags: None affected. Flags: None affected.
.Ss OR A,r8 .Ss OR A,r8
Store into Set
.Sy A .Sy A
the bitwise OR of the value in to the bitwise OR between the value in
.Ar r8 .Ar r8
and and
.Sy A . .Sy A .
@@ -1214,9 +1259,9 @@ Set if result is 0.
0 0
.El .El
.Ss OR A,[HL] .Ss OR A,[HL]
Store into Set
.Sy A .Sy A
the bitwise OR of the byte pointed to by to the bitwise OR between the byte pointed to by
.Sy HL .Sy HL
and and
.Sy A . .Sy A .
@@ -1228,9 +1273,9 @@ Bytes: 1
Flags: See Flags: See
.Sx OR A,r8 .Sx OR A,r8
.Ss OR A,n8 .Ss OR A,n8
Store into Set
.Sy A .Sy A
the bitwise OR of to the bitwise OR between the value
.Ar n8 .Ar n8
and and
.Sy A . .Sy A .
@@ -1249,10 +1294,10 @@ This is roughly equivalent to the following
.Em imaginary .Em imaginary
instructions: instructions:
.Bd -literal -offset indent .Bd -literal -offset indent
ld f, [sp] ; See below for individual flags LD F, [SP] ; See below for individual flags
inc sp INC SP
ld a, [sp] LD A, [SP]
inc sp INC SP
.Ed .Ed
.Pp .Pp
Cycles: 3 Cycles: 3
@@ -1278,10 +1323,10 @@ This is roughly equivalent to the following
.Em imaginary .Em imaginary
instructions: instructions:
.Bd -literal -offset indent .Bd -literal -offset indent
ld LOW(r16), [sp] ; C, E or L LD LOW(r16), [SP] ; C, E or L
inc sp INC SP
ld HIGH(r16), [sp] ; B, D or H LD HIGH(r16), [SP] ; B, D or H
inc sp INC SP
.Ed .Ed
.Pp .Pp
Cycles: 3 Cycles: 3
@@ -1297,10 +1342,10 @@ This is roughly equivalent to the following
.Em imaginary .Em imaginary
instructions: instructions:
.Bd -literal -offset indent .Bd -literal -offset indent
dec sp DEC SP
ld [sp], a LD [SP], A
dec sp DEC SP
ld [sp], flag_Z << 7 | flag_N << 6 | flag_H << 5 | flag_C << 4 LD [SP], F.Z << 7 | F.N << 6 | F.H << 5 | F.C << 4
.Ed .Ed
.Pp .Pp
Cycles: 4 Cycles: 4
@@ -1316,10 +1361,10 @@ This is roughly equivalent to the following
.Em imaginary .Em imaginary
instructions: instructions:
.Bd -literal -offset indent .Bd -literal -offset indent
dec sp DEC SP
ld [sp], HIGH(r16) ; B, D or H LD [SP], HIGH(r16) ; B, D or H
dec sp DEC SP
ld [sp], LOW(r16) ; C, E or L LD [SP], LOW(r16) ; C, E or L
.Ed .Ed
.Pp .Pp
Cycles: 4 Cycles: 4
@@ -1895,7 +1940,22 @@ Flags: See
.Sx SRL r8 .Sx SRL r8
.Ss STOP .Ss STOP
Enter CPU very low power mode. Enter CPU very low power mode.
Also used to switch between double and normal speed CPU modes in GBC. Also used to switch between GBC double speed and normal speed CPU modes.
.Pp
The exact behavior of this instruction is fragile and may interpret its second byte as a separate instruction
.Po see
.Lk https://gbdev.io/pandocs/Reducing_Power_Consumption.html#using-the-stop-instruction the Pan Docs
.Pc ,
which is why
.Xr rgbasm 1
allows explicitly specifying the second byte
.Pq Sy STOP Ar n8
to override the default of
.Ad $00
.Po a
.Sy NOP
instruction
.Pc .
.Pp .Pp
Cycles: - Cycles: -
.Pp .Pp
@@ -1982,7 +2042,9 @@ Bytes: 2
Flags: See Flags: See
.Sx SWAP r8 .Sx SWAP r8
.Ss XOR A,r8 .Ss XOR A,r8
Bitwise XOR between the value in Set
.Sy A
to the bitwise XOR between the value in
.Ar r8 .Ar r8
and and
.Sy A . .Sy A .
@@ -2003,7 +2065,9 @@ Set if result is 0.
0 0
.El .El
.Ss XOR A,[HL] .Ss XOR A,[HL]
Bitwise XOR between the byte pointed to by Set
.Sy A
to the bitwise XOR between the byte pointed to by
.Sy HL .Sy HL
and and
.Sy A . .Sy A .
@@ -2015,7 +2079,9 @@ Bytes: 1
Flags: See Flags: See
.Sx XOR A,r8 .Sx XOR A,r8
.Ss XOR A,n8 .Ss XOR A,n8
Bitwise XOR between the value in Set
.Sy A
to the bitwise XOR between the value
.Ar n8 .Ar n8
and and
.Sy A . .Sy A .