Question

Question: Provide the type, assembly language instruction, and binary representation of instruction described by the following MIPS fields: op=0, rs=3, rt=2, rd=3, shamt=0, funct=34

Short answer

This is a I type instruction

MIPS: lw $2, 4[$1]

Binary: 100011 00001 00010 0000000000000100

Step-by-step solution

Determine op=0:

op=0, rs=3, rt=2, rd=3, shamt=0, funct=34

this is R-type instruction

opcode :
The opcode is the machinecode representation of the instruction mnemonic. Several related instructions can have the same opcode. The opcode field is 6 bits long (bit 26 to bit 31).

Determine rs=3, rt=2, rd=3

rs, rt, rd:
The numeric representations of the source registers and the destination register. These numbers correspond to the $X representation of a register, such as $0 or $31. Each of these fields is 5 bits long. (25 to 21, 20 to 16, and 15 to 11, respectively). Interestingly, rather than rs and rt being named r1 and r2 (for source register 1 and 2), the registers were named "rs" and "rt" because t comes after s in the alphabet. This was most likely done to reduce numerical confusion.

Determine shamt=0

Shift (shamt):
Used with the shift and rotate instructions, this is the amount by which the source operand rs is rotated/shifted. This field is 5 bits long (6 to 10).

Determine Funct=34

Funct
For instructions that share an opcode, the funct parameter contains the necessary control codes to differentiate the different instructions. 6 bits long (0 to 5).
Example: Opcode 0x00 accesses the ALU, and the funct selects which ALU function to use

Converting MIPS fields to Assembly language

op=0 ---------> represents Add function. As several related instructions can have the same opcode we will consider the function also.
Funct =34 ------> converting decimal 34 to hexadecimal 0x22 which represent "sub" function.

ultimately ,the function which has opcode '0' and function '0x22' is "sub" function.

finally, the assembly level instruction is

sub $3, $3, $2

(rd rs rt)

conversion to binary format

R Format:

Converting an R mnemonic into the equivalent binary machine code is performed in the following way:

opcode	rs	rt	rd	shift	funct
6 bits	5 bits	5 bits	5 bits	5 bits	6 bits

opcode of sub is '0' and six bit long - 000000
rd,rs,rt,shift are five bit long so,
rd = $3 = 00011
rs = $3 = 00011
rt = $2 = 00010
shift = 0 = 00000
function is also six bit long ,funct = 34 = 100010

Now, put all binary numbers in a single line in the order mentioned above in the table that is your binary conversion of MIPS fields given;

000000 00011 00010 00011 00000 100010 ------> 621822(hexadecimal value)

op=0x23, rs=1, rt=2, const=0x4

op=0x23 represent " load word" i.e., lw
rs=1 represents "$1"
rt=2 represents "$2"
const=0x4

This is a I type instruction

MIPS: lw $2, 4[$1]

Binary: 100011 00001 00010 0000000000000100