main:
	li $a3, 0xffff0000  #base address of memory-mapped terminal

countdown: 
	li $s0, 3500000      #initialize time counter. Instruction rate is approximately one million instruction per second.
   

waitloop:                   #wait one second (500000)
	addi $s0,$s0,-1       
	bnez $s0,waitloop
	
CkReady:                      
	lw $t1,0($a3)       #read from receiver control registers
	andi $t1, $t1, 1    #extract ready bit
	beqz $t1, CkReady   
	lw $t0, 4($a3)      #get character from the keyboard

XReady:
	lw $t1,8($a3)       #read from transmitter control register
	andi $t1, $t1, 1    #extract ready bit
	beqz $t1, XReady    #if not ready branch back
	sw $t0, 12($a3)     #send character to display
      b countdown	        #wait one second until the other poll