Assembler Instructions:

Generic Format: optional_label  mneumonic  operands  line_documentation
Column:         1               10         16        up to 71

Some instructions set a 2 bit Condition Code (CC), which reflects the execution of an instruction.

RX Instructions: R - register, X - D(X,B) address format, 4 - bytes

1. Load

Format: label L R,D(X,B)

Copies the 4 bytes at the absolute address represented by D(X,B) into R. The previous contents of R are overwritten.

2. Store

Format: label ST R,D(X,B)

Stores the contents of R at the absolute address represented by D(X,B).

3. Add

Format: label A R,D(X,B)

Takes the 4 bytes from the absolute address represented by D(X,B) and adds it to the contents of R. The result is stored in R.

Sets the Condition Code.

  Code   Meaning
    0    Result is equal to 0
    1    Result is less than 0
    2    Result is greater than 0
    3    Overflow
  

4. Subtract

Format: label S R,D(X,B)

Takes the 4 bytes from the absolute address represented by D(X,B) and subtracts it from the contents of R. The result is stored in R.

Sets the Condition Code.

  Code   Meaning
    0    Result is equal to 0
    1    Result is less than 0
    2    Result is greater than 0
    3    Overflow
  

RR Instructions: 2 registers as the operands, 2 bytes

1. Load Register

Format: label LR R₁,R₂

Copies the contents of R₂ into R₁. The previous contents of R₁ are overwritten.

2. Add Register

Format: label AR R₁,R₂

Adds the contents of R₂ to R₁. Result is placed in R₁.

Sets the Condition Code.

  Code   Meaning
    0    Result is equal to 0
    1    Result is less than 0
    2    Result is greater than 0
    3    Overflow
  

3. Subtract Register

Format: label SR R₁,R₂

Subtracts the contents of R₂ from R₁. Result is placed in R₁.

Sets the Condition Code.

  Code   Meaning
    0    Result is equal to 0
    1    Result is less than 0
    2    Result is greater than 0
    3    Overflow