Homework 3 Computer Organization

Due: noon Friday, 2/14/03

1) Draw a 4-bit register that is able to perform the following operations:

• parallel read/output of all bits
• parallel write/input of all bits
• circular shift left (value shifted out of most-significant bit is shifted into the least-significant bit)
• circular shift right (value shifted out of least-significant bit is shifted into the most-significant bit)
• arithmetic shift right (sign-extend the most-significant bit)

2) Use the handout on the register file to draw a complete (not just a one-bit slice) register file that has:

• 4 registers
• 3-bits per register
• one write-port
• two read-ports

3) Consider the simple RISC Assembly Language:

Type of Instruction	Assembly Language	Register Transfer Language Description
Memory Access	Load R1, Mem
	Store R1, Mem	Mem[R1]
Move	Move R1, R2	R1 R2
	Move R1, #100	R1 100
Arithmetic Instruction (reg. operands only)	Add R1, R2, R3	R1 R2 + R3
	Sub R1, R2, R3	R1 R2 - R3
Conditional Branch	Compare R1, R2	Sets condition codes
	BGT LABEL (BLT, BLE, etc. too)	Branch to LABEL if conditions codes are set for <
Unconditional Branch	B LABEL	Always Branch to LABEL

What would the assembly language code for each of the programming statements be?

a) if (R2 < R3) then . else . end if	b) while (R2 < R4 and R2 >= 0) do . . . end while
c) repeat . . . until (R2 < R3)	d) for R2 = 0 to 100 by steps of size 5 do . . . end for