TOY_Assembly_Language_Spec.md

#The TOY Machine Language

The TOY language is an experimental ( educational ) assembly language target for TOY achitecture, and is a part of our final project C14-Assembler. Primary contributors to this project include: Andy , Tony and Borris.

##Directive

• .DATA
• .TEXT

Case-insensitive

##Data

• All variables must be declared within .DATA
• Declaration must abide to the following form: < variable name > < space > < value > where
  • < variable name > := An alphanumeric symbol with length no more than 10. It should not start with number. _ is allowed. For example: my_var is ok, while 0_0_My_Var is strictly forbidden.
  • < space > := A space or a tab.
  • < value > := Any integer within the range of -32,768 to +32,767 , i.e. 16 bits, signed integer, binary number unsupported. Prefix with 0x if the value is encoded hexadecimally. If you want to declare uninitialized value, set value to ?.
• Notice that size directive is not supported. By default, all variable must adopt to 16-bits, which correspond to WORD in Intel x86 syntax.

####Legal declaration

.DATA
   myVar 32766
   foo   -10
   bar   ?

##Instruction

####Data movements

• mov
• lea

####Arithmetic operations

• add
• sub
• inc
• dec

####Logical operations

• and
• xor
• shl
• shr

####Flow control

• jmp
• jz
• cmp

####Program counter operation

• call
• ret

####Stack operation

• push
• pop
• top

####IO

• read
• print

All instructions are case-insensitive

##Complete Instruction Specification

####Terminology

• <reg> := R<i> where i in range 1 to F. R case-sensitive. For example: R1, RA are valid register namerreby r1, R17 are invalid.
• <con8> := Any 8-bit integer.
• <con16> := Any 16-bit integer.
• <var> := Any variable declared in .data
• <mem> := [<reg>] [<var>] or [<con8>]. For example: [R1],[myVariable],[0xF8] are valid, but [ R1 ] is invalid.
• <instr> := Instruction.
• <dest> := Destination operand.
• <src> := Source operand.

####Rule

• Binary instructions: <instr> <dest> <src>. For example: mov R2 R1.
• Unary instructions: <instr> <src>. For example: inc R3.

---

####Mov

Move the content of <src> into the location referred to by <dest>

######Syntax

• mov <reg>,<reg>
• mov <reg>,<mem>
• mov <mem>,<reg>
• mov <reg>,<con16>
• mov <mem>,<con16>
• This is strictly forbidden: mov <mem> <mem>

---

####Lea

Write the address of <src> into <dest>. ( The content of <src> is unaffected. )

######Syntax

• mov <reg>,<mem>

---

####Add / Sub

Add <src> to <dest> / subtract <dest> by <src> and put the result into <dest>.

######Syntax

• add / sub <reg>,<reg>
• add / sub <reg>,<mem>
• add / sub <mem>,<reg>
• add / sub <reg>,<con16>
• add / sub <mem>,<con16>

---

##Symbol / label

• Label declaration never share common line with other instructions.

; This is OK.
loop1:          
   mov R1, R2
   
; This is not OK
loop2: mov R1, R2        

• Symbol can be referenced even before it's declared.
• Symbol contains only alphanumeric characters and _ and must not conflict with register name.
• Symbol name must not start with digits.
• A symbol must contains no more than 20 characters.

####Invalid symbol name

R8 ; conflicts with register name
myLongLongLongLongLongSymbol ; too long
2BeOrNot2Be ; starts with digit

##Comment

Anything prefixed by ; is regarded as comment and will not parsed by the assembler.