I don't see what Ada version of 6502 has over Nim's, see
<https://github.com/mratsim/glyph/blob/8b278c5/glyph/snes/datatypes.nim#L35-L89>
type
# Note using uint8 instead of machine word size will add zero-extending
overhead at every load
CPUStatusKind* = enum
Carry ## C - 0b00000001
Zero ## Z - 0b00000010
IRQ_Disabled ## I - 0b00000100
Decimal_Mode ## D - 0b00001000
Index8bit ## X - 0b00010000
Accum8bit ## M - 0b00100000
Overflow ## V - 0b01000000
Negative ## N - 0b10000000
Emulation_mode ## E - hidden / B - Break 0b00010000. Define if
6502 mode or 65816 mode
CpuRegs* = object
# General purpose registers
A*: uint16 ## Accumulator - Math register. Stores operands
or results of arithmetic operations.
X*, Y*: uint16 ## Index registers. Reference memory, pass
data, counters for loops ...
# Addressing registers
D*: uint16 ## Direct page addressing. Holds the memory
bank address of the data the CPU is accessing.
DB*: uint8 ## Data Bank. Holds the default bank for memory
transfers.
# Program control register
PB*: uint8 ## Program Bank. Holds the bank address of all
instruction fetches.
PC*: uint16 ## Program Counter. Address of the current
memory instruction.
SP*: uint16 ## Stack Pointer.
# Status register
P*: set[CPUStatusKind] ## Processor status
AddressingMode* = enum
# $number represents a number in hexadecimal representation
# Name # Example
Accumulator # dec a
Implied # clc
Immediate # inc #$12 or #$1234
Absolute # and $1234
AbsoluteLong # and $123456
AbsoluteLongX # and $123456,X
AbsoluteX # and $1234,X
AbsoluteY # and $1234,Y
AbsoluteXIndirect # jmp ($1234,X)
AbsoluteIndirect # jmp ($1234)
AbsoluteIndirectLong # jml [$1234]
Direct # and $12
DirectX # stz $12,X
DirectY # stz $12,Y
DirectXIndirect # and ($12,X)
DirectIndirect # and ($12)
DirectIndirectLong # and [$12]
DirectIndirectY # and ($12),Y
DirectIndirectLongY # and [$12],Y
ProgramCounterRelative # beq $12
ProgCountRelativeLong # brl $1234
StackRelative # and $12,S
StackRelativeIndirectY # and ($12,S),Y
BlockMove # mvp $12, $34
Cpu* = object
regs*: CpuRegs
cycles*: int
Run
