assembly w/ Mars

(Memory mapped I/O polling) Write a MIPS program to implement the following single digit adder:

keyboard input: X+Y=

display output: X+Y=Z

where X and Y are single digits (such as 2 and 7) and Z is the result (such as 9). A possible way to implement:

1. Polling on the receiver control and read the byte from the receiver data. Doing this for four times so that the four characters X, +, Y, = are stored in an array.

2. Compute the result Z. You need find your own way of converting the ascii byte for a digit into the value of the digit so that the value of Z can be computed. Store the ascii bytes (the result Z might have two digits) into the array.

3. Polling on the transmitter control and write into the transmitter data so that the experssion (such as 5+7=12) is sent to the display.

4. To test your code, you need open the MMIO in the simulator. Goto Tools?Keyboard and Display MMIO ? make sure you press connect to MIPS to run your code. Sometimes, it is also helpful to press reset on the same screen.

5. Hint: a way to convert a byte storing a single digit into the value of the digit, and the converse (my code is untested)

char2num:

lb $t0, asciiZero

subu $v0, $a0, $t0

jr $ra

num2char:

lb $t0, asciiZero

addu $v0, $a0, $t0

jr $ra

.data

asciiZero: .byte 0

exp: .byte 30