안녕하세요 혹시 mips사용하시는 분들 계신가요?

안녕하세요. 다름이 아니라 MIPS를 David A.Patterson, John L.henness의 Computer Organization&Design이 책으로 공부하는 중인데요. CD에 있는 project중에

Write a subroutine, wait, that will wait until the button K2 is pressed, then wait until the button is released, and finally, return. It should read from the address 0xbfa00000 until it receives a 1 in bit position 0 from this read operation. Next, it should read until the bit becomes zero again, and then return. This method of receiving 2 information from the outer world is called polling. The subroutine should be called with the instruction jal wait, as shown in the main program above.

#include

.set noreorder
.text
.globl start
.ent start

start : jal wait # Wait for button click
nop
lui s0, 0xbf90 # Load switch port address
lb s1, 0x0(s0) # Read first number from switches
nop
jal wait # Wait for button click
nop
lb s2, 0x0(s0) # Read second number from switches
nop
addu s3, s1, s2 # Perform an arithmetic operation
sb s3, 0x0(s0) # Write the result to LEDs
jal finish
nop

b start

nop

wait :(여기 빈칸의 인스트럭션을 채워야 하는데요...)

finish : lui t2, 0xbfa0

lb t3, 0x0(t2)

nop

sb t3, 0x0(t2)

nop

bnez t3, k3

nop

b finish

nop

k3 : lui t2. 0xbfa0

lb t3, 0x0(t2)

nop

sb t3, 0x0(t2)

nop

bnez t3, k3

nop

jr ra

.end start

이 문제를 어떻게 풀어야할지 도저히 모르겠어서 도움을 요청해 봅니다:)