Question

Assume that the program counter (PC) is set to 0x00000000. Describe how each of the instructions below could be used to set the next value of PC to 0x0FFFFFF4

j, jr, bne, jal, beq

Answer 1

solution:

given data:

Assume that the program counter (PC) :

j and jal instructions:

• The main J-type directions are the hop guidelines j and jal. These guidelines require a 26-piece coded address field to determine the objective of the hop.
• At the point when a J-type guidance is executed, an entire 32-digit hop target address is shaped by connecting the high request four pieces of the PC (the location of the guidance following the hop), the 26 pieces of the objective field, and two 0 pieces

Format Opcodes

op 31-26

target 25-0

Instruction	Opcode	Target
j	label	000010	coded address of label
jal	label	000011	coded address of label

JR instruction:

• The jr guidance returns control to the guest. It duplicates the substance of $ra into the PC: jr $ra # PC <― $ra # A branch delay # opening adheres to this guidance. Normally you think about this as "hopping to the location in $ra ."
• The Jump Register guidance makes the PC hop to the substance of the first source register.

• The sample JR instruction demonstrated in the datapath above is JR $13.

  The instruction's equivalent in binary is:

(opcode) (rs) (rt) (rd) (shamt) (funct)

000000 01101 00000 00000 00000 001000

BNE instrction:

• BNE (another way to say "Branch if Not Equal") is the mental helper for a machine language guidance which branches, or "hops", to the location indicated if, and just if the zero banner is clear.

• In the event that the Z banner of the CCR is clear, the destination operand will be added to the PC, and the 68k will keep perusing at the new balanced held in PC. If the Z banner is set, the guidance is disregarded.

beq instruction:

• BEQ (another way to say "Branch if EQual") is the mental aide for a machine language guidance which branches, or "bounces", to the location indicated if, and just if the zero banner is set.
• The BEQ guidance branches the PC if the primary source register's substance and the subsequent source register's substance are equivalent.

It's linguistic structure is:

BEQ $first source register's location, $second source register's location, branch esteem.

The example BEQ guidance showed in the datapath above is BEQ $9, $11, .

The guidance's identical in binary is:

(opcode) $rs $rt (offset)

000100 01011 01011

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