我的LC-3程序如何导致无限循环？

Question

我的JSR调用了按预期功能的子例程，但是，当我测试程序时，它被卡在无限的循环中，我不确定为什么。有人可以把我指向正确的方向吗？

这是子例程应该要做的：

 Input: NUM     (r0, a positive integer)
 Output: STEPS  (r1, the required number of steps for calculation)

 STEPS = 0

 while NUM is not equal to 1:
 if NUM is even -> reduce NUM to NUM/2
 if NUM is odd  -> increase NUM to 3 * NUM + 1
 increment STEPS by 1

这是我的子例程：

AND R1, R1, #0             ; INSTANTIATING R1 TO 0 TO RESOLVE REG CONFLICT
ST R0, R0SAVE      
ST R1, R1SAVE

NUM1LOOP  LD R1, R1SAVE
ADD R1, R1, #1
ST R1, R1SAVE
LD R1, ONE               ;Loads 1 into R1 to compare to N
NOT R1, R1
ADD R1, R1, #1
ADD R0 R0, R1        ; CHECKS TO SEE IF N >=1
BRz DONE             ; IF N = 0, N IS 1 AND NEEDS TO STOP LOOP, ELSE CONT.

CHECKEO      AND R0, R1, #1
BRz DIV2E
AND R1, R1,  #0
JSR MUL3ADD1
ST R1, R1JSR
ST R0, R1JSR
BRnzp NUM1LOOP




DIV2E       AND R1, R1,  #0
JSR  DIVIDEBY2
ST R1, R1JSR
ST R0, R1JSR
BRnzp NUM1LOOP      
    
DONE         LD R1, R1SAVE


R1JSR      .BLKW #1
R0SAVE .BLKW #1
R1SAVE .BLKW #1
ONE .FILL #1
RET