Glossary

ASM (Super NES Programming/65c816 reference) [1]

Internal Registers

Register	Description
A	The accumulator. This is the math register. It stores one of two operands or the result of most arithmetic and logical operations.
X, Y	The index registers. These can be used to reference memory, to pass data to memory, or as counters for loops.
S	The stack pointer, points to the next available(unused) location on the stack.
DBR	Data bank register, holds the default bank for memory transfers.
D	Direct page register, used for direct page addressing modes.
PBR	Program Bank, holds the bank address of all instruction fetches.
P	Processor Status, holds various important flags, see below.

Flags stored in P register

Mnemonic	Name	Value	Binary Value
N	[N]egative	#$80	10000000
V	O[v]erflow	#$40	01000000
-	-	#$20	00100000
B	[B]reak	#$10	00010000
D	[D]ecimal	#$08	00001000
I	[I]nterrupt	#$04	00000100
Z	[Z]ero	#$02	00000010
C	[C]arry	#$01	00000001

Branch Instructions

Instruction	Description	Flags	Notes
BRA	Branch Always	-	unconditional
BRL	Branch Always Long	-	unconditional
BPL	Branch if plus < 80h	N	N=0
BMI	Branch if minus >= 80h	N	N=1
BVC	Branch if overflow flag is clear	V	V=0
BVS	Branch if overflow flag is set	V	V=1
BNE	Branch if Not Equal to zero	Z	Z=0
BEQ	Branch if Equal to zero	Z	Z=1
BCC	Branch if Carry Flag is Clear	C	C=0
BCS	Branch if Carry Flag is Set	C	C=1

Arithmetic and Logical Instructions

Instruction		Flags set	Arguments
ADC	Add A with something and carry bit. Result is put in A.	n,v,z,c	Immediate value or address
SBC	Subtract something and the carry bit.	n,v,z,c
AND	AND A with memory, storing result in A.	n, z	Immediate value or address
EOR	Exclusive or	n, z
ORA	OR A with memory, storing result in A.	n, z	Immediate value or address
TSB	Test and set bits	z
TRB	Test and reset bits	z
ASL	Arithmetic shift left	n, z,c	A or address
LSR	Logical shift right	n, z,c	A or address
ROL	Rotate left	n, z,c	A or address
ROR	Rotate right	n, z,c	A or address
BIT	test bits, setting	n,v,z (only z if in immediate mode)	immediate value or address
CMP	Compare accumulator with memory	n, z,c
CPX	Compare register X with memory	n, z,c
CPY	Compare register Y with memory	n, z,c
DEA	Decrement Accumulator	n, z
DEC	Decrement, see INC	n, z
DEX	Decrement X register	n, z
DEY	Decrement Y register	n, z
INA	Increment Accumulator	n, z
INC	Increment, see DEC	n, z
INX	Increment X register	n, z
INY	Increment Y register	n, z
XBA	Exchange bytes of accumulator	n, z
NOP	No operation	none

Load/Store Instructions

Instruction	Description
LDA	Load accumulator from memory
LDX	Load register X from memory
LDY	Load register Y from memory
STA	Store accumulator in memory
STX	Store register X in memory
STY	Store register Y in memory
STZ	Store zero in memory

Transfer Instructions

Instruction	Description	Flags
TAX	Transfer Accumulator to index register X	n,z
TAY	Transfer Accumulator to index register Y	n,z
TCD	Transfer 16-bit Accumulator to Direct Page register	n,z
TCS	Transfer 16-bit Accumulator to Stack Pointer	none
TDC	Transfer Direct Page register to 16-bit Accumulator	n,z
TSC	Transfer Stack Pointer to 16-bit Accumulator	n,z
TSX	Transfer Stack Pointer to index register X	n,z
TXA	Transfer index register X to Accumulator	n,z
TYA	Transfer index register Y to Accumulator	n,z
TXS	Transfer index register X to Stack Pointer	none
TYX	Transfer index register Y to index register X	n,z
TXY	Transfer index register X to index register Y	n,z

Jump and call instructions

Instruction	Description
JMP	Jump
JML	Jump long
JSR	Jump and save return address
JSL	Jump long and save return address
RTS	Return from subroutine
RTL	Return long from subroutine

Interrupt instructions

Instruction	Description
BRK	Generate software interrupt
COP	Generate coprocessor interrupt
RTI	Return from interrupt
STP	Stop processor until RESET
WAI	Wait for hardware interrupt

P Flag instructions

Instruction	Description	Notes
CLC	Clear carry flag
CLD	Select binary arithmetic
CLI	Enable interrupt requests
CLV	Clear overflow flag
REP	Reset status bits	(for example REP 0x00100000 clears the M flag)
SEC	Set carry flag
SED	Select decimal arithmetic
SEP	Set status bits	(for example SEP 0x00010000 sets the X flag)
SEI	Disable interrupt requests
XCE	Exchange carry flag with emulation flag

Stack Instructions

Instruction	Description
PHA	Push Accumulator
PHX	Push index register X
PHY	Push index register Y
PHD	Push direct page register
PHB	Push data bank register
PHK	Push Program Bank Register
PHP	Push processor status
PEA	Push effective address
PEI	Push effective indirect address
PER	Push effective relative address
PLA	Pull Accumulator
PLX	Pull index register X
PLY	Pull index register Y
PLP	Pull processor status
PLD	Pull direct page register
PLB	Pull data bank register

Technicalities

Acronym	Meaning	Description
DMA	Direct Memory Access	basically a piece of hardware that allows I/O devices to copy to and from main memory independently of CPU control
HDMA	H-Blank Direct Memory Access
NMI [2]	non-maskable interrupt
IRQ	Interrupt Request