Assembly Language

TRC Video

https://www.youtube.com/watch?v=D9rxI2hVEfQ

Example Programs

Assembly Language Multiplication

Assembly Language Division

Assembly Language IF

Assembly Language IF ELSE

Assembly Language DO WHILE

Assembly Language FOR

Assembly Language WHILE

Assembly Language Check for ODD / EVEN

Assembly Language Twos Complement

Assembly Language Logical Shift

Operands

The operand can be interpreted in two different ways, if it uses:

• # it refers to a specific value to use
• Rm uses the value stored in register m

Op Codes

Below is a list of the OpCodes used within your examinations. This table will always be given to you with a small explanation and syntax for each command.

LDR - Load

This instruction is to load a value stored in memory into a CPU register.

LDR Rd, <memory ref>

STR - Store

This instruction is to store a value from Register d into Memory location <memory ref>.

STR Rd, <memory ref>

ADD - Add

Operation used to add two numbers together, the value in the operand to the value in Register n.

The output is stored in Register d

ADD Rd, Rn, <operand>

SUB - Subtract

operation used to subtract two numbers from each other, the value in the operand from the value in Register n.

The output is stored in Register d

SUB Rd, Rn, <operand>

MOV - Move

This instruction is to copy a value into a register. The value from the operand is stored in Register d

MOV Rd, <operand>

CMP - Compare

The CMP instruction compares two operands. It is generally used in conditional execution and is needed if you wish to do a conditional branch. It compares the operand with the Register n.

CMP Rn, <operand>

B - Branch

This will always branch to the instruction at position <label> in the program.

B <label>

BEQ - Branch If Equal

This must follow a CMP, and if the CMP values are equal this OpCode will branch to the specified <label>

BEQ <label>

BNE - Branch If Not Equal

This must follow a CMP, and if the CMP values are not equal this OpCode will branch to the specified <label>

BNE <label>

BGT - Branch If Greater Than

This must follow a CMP, and if the CMP values are Greater Than this OpCode will branch to the specified <label>

BGT <label>

BLT - Branch If Less Than

This must follow a CMP, and if the CMP values are Less Than this OpCode will branch to the specified <label>

BLT <label>

AND - Bitwise And

This OpCode will perform a bitwise logical AND between the values in Register n and the <operand>.

This will compare both inputs, it will output a 1 for each bit when both inputs are a 1. All other outputs will be a 0

The result is stored in Register d

AND Rd, Rn, <operand>

ORR - Bitwise Or

This OpCode will perform a bitwise logical OR between the values in Register n and the <operand>.

This will compare both inputs, it will output a 1 for each bit when either inputs are a 1. All other outputs will be a 0

The result is stored in Register d

ORR Rd, Rn, <operand>

EOR - Bitwise Xor

This OpCode will perform a bitwise logical XOR between the values in Register n and the <operand>.

This will compare both inputs, it will output a 1 for each bit when either but not both inputs are a 1. All other outputs will be a 0

The result is stored in Register d

EOR Rd, Rn, <operand>

MVN - Bitwise Not

This OpCode will perform a bitwise logical NOT between the value in the <operand>.

This will negate the input by swapping all 1's for 0's, and 0's for 1's

The result is stored in Register d

MVN Rd, <operand>

LSL - Logical Shift Left

Logically shift left the value stored in Register n by the number of bits specified by the <operand>.

The result is stored in Register d

Logical shifts can be useful as efficient ways to perform multiplication or division of unsigned integers by powers of two. Shifting left by n bits on a signed or unsigned binary number has the effect of multiplying it by 2_n.

LSL Rd, Rn, <operand>

LSR - Logical Shift Right

Logically shift right the value stored in Register n by the number of bits specified by the <operand>.

The result is stored in Register d

Logical shifts can be useful as efficient ways to perform multiplication or division of unsigned integers by powers of two. Shifting right by n bits on an unsigned binary number has the effect of dividing it by 2_n (rounding towards 0).

LSR Rd, Rn, <operand>

HLT - Halt Program

Causes the processor to stop executing your program.

HLT