My MARIE Simulator wont terminate when period is entered. For the life of me I dont know where I am going wrong on this. The assignment is to create a assembly language program that can do the following: "You are to design, write, test, and debug a MARIE assembly language program that inputs a sequence of characters from the set A$-$Z $($capital letters only$),$ stores each character in memory after it is transformed by the trivial ROT$13$ cipher, and then, after character input completes, outputs the transformed characters".

Here is the code I currently have so far:

$/$ Starting Code: Initialization

ORG $100$

$/$ Initialize Ptr $($pointer$)$

Load Start

Store Ptr

$/$ Main Program

MainLoop, Input $/$ Input a character

Store InVal $/$ Store input in InVal

Load InVal $/$ Load input value to AC

Subt ChPer $/$ Check if input is a period

Skipcond $400/$ If AC $==0($input is $\text{'}.\text{'}),$ jump to OutputStart

Jns ROT$13/$ Call ROT$13$ subroutine to transform the character

StoreI Ptr $/$ Store the transformed character in memory

Load Ptr $/$ Load pointer address

Add One $/$ Increment pointer

Store Ptr $/$ Store updated pointer

Jump MainLoop $/$ Repeat the input loop

$/$ Output Phase

OutputStart, Load Start $/$ Initialize pointer to the start of stored characters

Store Ptr

OutputLoop, LoadI Ptr $/$ Load the character from memory

Subt ChPer $/$ Check if the character is $\text{'}.\text{'}$

Skipcond $400/$ If AC $==0($character is $\text{'}.\text{'}),$ jump to EndProgram

Output $/$ Output the character

Load Ptr $/$ Load pointer address

Add One $/$ Increment pointer

Store Ptr $/$ Store updated pointer

Jump OutputLoop $/$ Repeat the output loop

EndProgram, Halt $/$ End the program

$/$ Starting Code: ROT$13$ Subroutine

ROT$13,$ HEX $0$

Load InVal

Add Val$13$

Store Hold

Subt ChZ

Skipcond $800$

Jump NoAdj

Add ChA

Jump Done

NoAdj, Load Hold

Done, JumpI ROT$13$

$/$ Starting Code: Constants, Data Area

$/-----$

$/$ Constants $($the program should not write to these locations$)$

$/-----$

ChA, HEX $0041/$ Constant value $\text{'}$A$\text{'}$

ChZ$,$ HEX $005$A $/$ Constant value $\text{'}$Z$\text{'}$

ChPer, HEX $002$E $/$ Constant period char $\text{'}.\text{'}$

Val$13,$ DEC $13/$ Constant ROT$13$ value

One, HEX $1/$ Constant value $1$

Start, HEX $200/$ Constant address for starting memory location

$/-----$

$/$ Data area $($these locations are for reading and writing$)$

$/-----$

InVal, HEX $0/$ Subroutine input value

Hold, HEX $0/$ Temporary variable

Ptr$,$ HEX $0/$ Character pointer

Whenever I enter a period and get to the SKIPCOND $400$ step it correctly identifies the value is zero but still takes it as input instead of moving to the output phase. Any help in figuring out where my issue lies would be greatly appreciated.