Comp Sci LC3 ISA

LC-3 instructions, select the best description of what it does. "NOT"

Inverts each bit of a value stored in register.

If the condition code values are N=1, Z=0, and P=0, which of the below statements is true about the most recent operation that updated the condition codes?

Negative

If the condition code values are N=0, Z=0, and P=1, which of the below statements is true about the most recent operation that updated the condition codes?

Positive

If the condition code values are N=1, Z=0, and P=0, which of the below statements is true about the most recent operation that updated the condition codes?

The operation placed a negative value into a register.

If the condition code values are N=0, Z=1, and P=0, which of the below statements is true about the most recent operation that updated the condition codes?

Zero

What would be a good name for a signal connected to output 1 of the above decoder?

isADD

What would be a good name for a signal connected to output 5 of the above decoder?

isAND

The name of the signal connected to the output is named ____ because that output of the decoder is only 1 (true) when the instruction in the IR is a BR instruction, and is 0 (false) when the IR holds any other type of instruction that is not a BR instruction.

isBR

What would be a good name for a signal connected to output 9 of the above decoder?

isNOT

For a BR instruction, output ____ of the decoder will be equal to ____ and all other decoder outputs will be equal to ____.

0 1 0

A signal named isLDI should be connected to which decoder output?

10

A signal named isSTI should be connected to which decoder output?

11

The DR signal (connected to the DA input of the register file) comes from IR[______] but the value of that 3-bit signal only matters when writing to register.

11:9

A signal named isLD should be connected to which decoder output?

2

By looking at the ADD and AND instructions on the LC-3 Instruction Set sheet, we can see that the SR2 signal (the address of source register 2) should be connected to IR[____].

2:0

A signal named isST should be connected to which decoder output?

3

BMUX is value at position? (in ADD, AND, NOT)

5

A signal named isLDR should be connected to which decoder output?

6

A signal named isSTR should be connected to which decoder output?

7

By looking at the ADD and AND instructions on the LC-3 Instruction Set sheet, we can see that the SR1 signal (the address of source register 1) should be connected to IR[____].

8:6

LC-3 instructions, select the best description of what it does. "ADD"

Adds contents of two registers, or one register and one sign-extended constant.

LC-3 instructions, select the best description of what it does. "AND"

Bitwise ANDs values in two registers, or one register and one sign-extended constant.