NES Assembly Language

CPU Registers

A	Accumulator
X	Index
Y	Index

 

Number Literal

literal在日语中被翻译成「直定数」，似乎比有些中文译本中的“字面值”更好理解。既可以理解成“直接定义的数”，从开发者的角度；也可以理解成“直接能确定的数”，从编译器的角度。

Syntax：

#<radix modifier>number

<radix modifier>:: $ | % | NULL

‘$’ symbol means the number is in hexadecimal

‘%’ symbol means the number is in binary

‘NULL’ means the number is in decimal

‘#’ symbol means immediate value

Addressing

address is 16bits

Direct Addressing

Syntax: ($)?<address>

‘$’ symbol means the address is in hexadecimal

 

Instructions

LDA, LDX, LDY

将立即数，内存单元中的值写入寄存器

STA, STX, STY

将寄存器中的值存到内存单元