HW7: Final Changes

14 files changed, 655 insertions, 75 deletions

diff --git a/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell.mcp b/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell.mcp
index df45c48..9377caf 100644
--- a/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell.mcp
+++ b/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell.mcp
diff --git a/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell_Data/CWSettingsWindows.stg b/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell_Data/CWSettingsWindows.stg
index 60d7785..d39991e 100644
--- a/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell_Data/CWSettingsWindows.stg
+++ b/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell_Data/CWSettingsWindows.stg
diff --git a/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell_Data/Standard/TargetDataWindows.tdt b/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell_Data/Standard/TargetDataWindows.tdt
index 6a2215a..f0b3cf3 100644
--- a/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell_Data/Standard/TargetDataWindows.tdt
+++ b/cmpen472_hw8McDonnell/cmpen472_hw8McDonnell_Data/Standard/TargetDataWindows.tdt
diff --git a/cmpen472hw7_McDonnell/Full_Chip_Simulation.ini b/cmpen472hw7_McDonnell/Full_Chip_Simulation.ini
index 31a4a6c..93f96db 100644
--- a/cmpen472hw7_McDonnell/Full_Chip_Simulation.ini
+++ b/cmpen472hw7_McDonnell/Full_Chip_Simulation.ini
@@ -10,7 +10,7 @@ Target=sim
 Layout=ASM_layout.hwl
 LoadDialogOptions=AUTOERASEANDFLASH NORUNAFTERLOAD
 CPU=HC12
-MainFrame=0,1,-1,-1,-1,-1,663,183,2320,1195
+MainFrame=0,1,-1,-1,-1,-1,564,171,1983,1183
 TOOLBAR=57600 57601 32795 0 57635 57634 57637 0 57671 57669 0 32777 32776 32782 32780 32781 32778 0 32806
 Configuration=Full_Chip_Simulation.hwc
 Statusbar=1
diff --git a/cmpen472hw7_McDonnell/Sources/cmpen472hw7_McDonnell.asm b/cmpen472hw7_McDonnell/Sources/cmpen472hw7_McDonnell.asm
new file mode 100644
index 0000000..2ea61a0
--- /dev/null
+++ b/cmpen472hw7_McDonnell/Sources/cmpen472hw7_McDonnell.asm
@@ -0,0 +1,600 @@
+**************************************************************************
+*
+* Title:        Calculator
+*
+* Objective:    CMPEN 472 Homework 7
+*
+* Revision:     V1.0
+*
+* Date:         Mar. 17, 2025
+*
+* Programmer:   Jacob McDonnell
+*
+* Company:      The Pennsylvania State University
+*               Department of Computer Science and Engineering
+*
+* Algorithm:    Simple Serial I/O, ASCII to decimal conversion, & basic math
+*
+* Register Use: A & B to current byte, etc,
+*               X & Y holds address of strings and length of string,
+*               D & Y for arithmatic.
+*
+* Memory Use:   RAM Locations from $3000 for data,
+*               RAM Locations from $3100 for program
+*
+* Input:        Serial Port for User Input
+*
+* Output:       Serial Port for String Output
+*               Memory locations changed if modified by user
+*
+* Observation:  This program is a simple 16-bit calculator. The input can be
+*               any 4 digit positive decimal integer, the output can be negative.
+*               The +, -, *, and / operators are supported. Only two numbers at
+*               a time.
+*
+* Note:         ON CSM-12C128 board,
+*
+* Comments:     This program is developed and simulated using CodeWarrior
+*               development software and targeted for Axion
+*               Manufacturing's CSM-12C128 board running at 24MHz.
+*
+**************************************************************************
+* Parameter Declearation Section
+*
+* Export Symbols
+            xdef        pgstart         ; export 'pgstart' symbol
+            absentry    pgstart         ; for assembly entry point
+
+* Symbols and Macros
+PORTA       equ         $0000           ; i/o port A addresses
+DDRA        equ         $0002           ; data direction register for PORTA
+PORTB       equ         $0001           ; i/o port B addresses
+DDRB        equ         $0003           ; data direction register for PORTB
+
+SCIBDH      equ         $00C8           ; Serial port (SCI) Baud Register H
+SCIBDL      equ         $00C9           ; Serial port (SCI) Baud Register L
+SCICR2      equ         $00CB           ; Serial port (SCI) Control Register 2
+SCISR1      equ         $00CC           ; Serial port (SCI) Status Register 1
+SCIDRL      equ         $00CF           ; Serial port (SCI) Data Register
+
+CR          equ         $0d             ; carriage return, ASCII 'Return' key
+LF          equ         $0a             ; line feed, ASCII 'next line' character
+NULL        equ         $00             ; NULL Terminator character
+
+**************************************************************************
+* Data Section: address used [ $3000 to $30FF ] RAM Memory
+*
+            org         $3000           ; Reserved RAM memory starting address
+                                        ;   for Data for CMPEN 472 class
+numBuf      dc.w        $0000           ; Memory location for addition and subtraction
+                                        ;   in Solve subroutine
+
+operator    dc.b        $0000           ; Operator character for VerifyInput
+
+buffer      ds.b        $0010           ; Array of 16 bytes to read a string
+            dc.b        NULL            ; NULL terminated
+lenBuf      dc.w        $0010           ; Length of buffer array
+
+buffer2     ds.b        $0010           ; Array of 16 bytes for reading and reversal
+            dc.b        NULL            ; NULL terminated
+lenBuf2     dc.w        $0010           ; length of buffer2
+
+*
+* There is a section Data Section at the end of the file
+**************************************************************************
+* Program Section: address used [ $3100 to $3FFF ] RAM Memory
+*
+            org         $3100           ; Program start address, in RAM
+pgstart     lds         #$3100          ; initialize the stack pointer
+
+            ldaa        #%11110001      ; LED 1,2,3,4 at PORTB bit 4,5,6,7
+            staa        DDRB            ; set PORTB bit 4,5,6,7 as output
+
+            ldaa        #$0C            ; Enable SCI port Tx and Rx units
+            staa        SCICR2          ; disable SCI interrupts
+
+            ldd         #$0001          ; Set SCI Baud Register = $0001 => 1.5M baud at 24MHz (for simulation)
+            std         SCIBDH          ; SCI port baud rate change
+
+            ldx         #msg            ; Load the address of the welcome message into X
+            jsr         WriteString     ; Write the string to the serial console
+
+mainLoop
+            ldx         #buffer         ; Load the address of the buffer into X
+            ldy         lenBuf          ; Load the length of the buffer into Y
+            jsr         Zeros           ; Fill the buffer with zeros
+
+            ldx         #prompt         ; Load Address of prompt string into X
+            jsr         WriteString     ; Write string to serial console
+
+            ldx         #buffer         ; Load the address of the buffer into X
+            ldy         lenBuf          ; Load the length of the buffer into Y
+            jsr         ReadString      ; Read a line from the serial console
+
+            ldx         #buffer         ; Load the address of the buffer into X
+            jsr         VerifyInput     ; Verify user input
+            beq         mainLoop        ; Invalid input, jump back to loop
+
+            ldx         #buffer         ; Load the address of the buffer into X
+            jsr         Solve           ; Jump to Solve to solve the user input
+            bra         mainLoop        ; Loop back to mainLoop always
+
+**************************************************************************
+* Subroutine Section: address used [ $3100 to $3FFF ] RAM Memory
+*
+
+;*************************************************************************
+; Solve subroutine
+;
+; This subroutine will solve the math equation in the given string.
+;
+; Input:                   Address of null terminated string in X.
+; Output:                  No Output, Control flow changed to proper subroutine.
+; Registers in use:        X for the address of the string, A & B to read characters from
+;                          from the string.
+; Memory locations in use: Memory Address for serial line, address of the string, numBuf word
+;
+; Comments: This subroutine EXPECTS the input to be valid. RUN VerifyInput BEFORE
+;           TO MAKE SURE THE STRING IS VALID, OTHERWISE THERE WILL BE ERRORS.
+;
+
+Solve
+            pshy                        ; Save Y to the stack
+            pshd                        ; Save D to the stack
+            pshx                        ; Save X to the stack
+            jsr         ReadDecimal     ; Read First number
+            pshy                        ; Save Y to the stack
+            ldaa        -1,x            ; Read operator from X and save to A
+            jsr         ReadDecimal     ; Read First number
+            cmpa        #'+'            ; Compare A to '+'
+            beq         sAdd            ; Jump to sAdd to add the numbers
+            cmpa        #'-'            ; Compare A to '-'
+            beq         sSub            ; Jump to sSub to add the numbers
+            cmpa        #'*'            ; Compare A to '*'
+            beq         sMul            ; Jump to sMul to add the numbers
+            exg         y,x             ; Exchange X and Y
+            puly                        ; Restore Y from the stack
+            exg         y,d             ; Exchange Y and D
+            idiv                        ; Divide D/X => X
+            exg         x,d             ; Exchange X & D
+            bra         sDone           ; Jump to sDone
+sAdd        sty         numBuf          ; Save Y to numBuf
+            puly                        ; Restore Y from the stack
+            exg         y,d             ; Exchange Y and D
+            addd        numBuf          ; Add D and numBuf
+            bra         sDone           ; Jump to sDone
+sSub        sty         numBuf          ; Save Y to numBuf
+            puly                        ; Restore Y from the stack
+            exg         y,d             ; Exchange Y and D
+            subd        numBuf          ; Subtract D and numBuf
+            bra         sDone           ; Jump to sDone
+sMul        exg         y,d             ; Exchange Y and D
+            puly                        ; Restore Y from the stack
+            emul                        ; Multiply Y*D => Y:D
+            cpy         #0              ; Compare Y to 0
+            bne         sOverflow       ; If Y != 0, Overflow
+sDone       cpd         #9999           ; Compare D to 9999 (Max output)
+            bgt         sOverflow       ; Branch to sOverflow if D > 9999
+            cpd         #-9999          ; Compare D to -9999 (Min output)
+            blt         sOverflow       ; Branch to sOverflow if D < -9999
+            pulx                        ; Restore X from the stack
+            jsr         WriteString     ; Write original equation to serial console
+            psha                        ; Save A to the stack
+            ldaa        #'='            ; Load '=' into A
+            jsr         putchar         ; Print '=' to serial console
+            pula                        ; Restore A from the stack
+            ldy         #buffer         ; Load address of buffer into Y
+            jsr         PrintDecimalWord; Print the answer to the Serial console
+            ldaa        #CR             ; Load CR into A
+            jsr         putchar         ; Jump to putchar to write CR
+            ldaa        #LF             ; Load LF into A
+            jsr         putchar         ; Jump to putchar to write CR
+            puld                        ; Restore D from the stack
+            puly                        ; Restore Y from the stack
+            rts                         ; Return to caller
+sOverflow   pulx                        ; Restore X from the stack
+            pshx                        ; Save X to the stack
+            jsr         WriteString     ; Write original string to serial console
+            ldaa        #CR             ; Load CR into A
+            jsr         putchar         ; Jump to putchar to write CR
+            ldaa        #LF             ; Load LF into A
+            jsr         putchar         ; Jump to putchar to write CR
+            ldx         #overflow       ; Load address of overflow string into X
+            jsr         WriteString     ; Write overflow string to serial
+            pulx                        ; Restore X from the stack
+            puld                        ; Restore D from the stack
+            puly                        ; Restore Y from the stack
+            rts                         ; Return to caller
+
+;*************************************************************************
+; VerifyInput subroutine
+;
+; This subroutine will verify the user input is valid.
+;
+; Input:                   An address of a Null terminated string in register X.
+; Output:                  If valid Zero bit = 0 in CCR, if invalid, Zero bit = 1
+;                          and the string is outputed up to the error on the serial
+;                          console with an error message.
+; Registers in use:        X for the address of the string, A for reading characters.
+;                          Y to count the number of digits in a number, & B to count the number of numbers
+; Memory locations in use: Memory Address for serial line, address of the string, 1 byte for operator
+;
+; Comments: This subroutine will modify the user string if invalid.
+;
+
+VerifyInput
+            pshy                        ; Save Y to the stack
+            pshd                        ; Save D to the stack
+            pshx                        ; Save X to the stack
+            clrb                        ; Set B to Zero
+            stab        operator        ; Clear operator
+            ldy         #0              ; Load Zero into Y
+vNumLoop    ldaa        1,x+            ; Load character from X into A
+            cmpa        #'9'            ; Compare A to '9'
+            bhi         vInvalid        ; If A > '9', not valid string
+            cmpa        #'0'            ; Compare A to '0'
+            blt         vIsOp           ; If A < '0', check if operator
+            iny                         ; Increment Y by 1 to count numbers
+            cpy         #4              ; Compare Y to 4
+            bhi         vInvalid        ; If greater than 4, invalid
+            bra         vNumLoop        ; Loop back to check for more digits
+vIsOp       cmpa        #'+'            ; Compare A to '+'
+            beq         vOp             ; This is an operator
+            cmpa        #'-'            ; Compare A to '-'
+            beq         vOp             ; This is an operator
+            cmpa        #'*'            ; Compare A to '*'
+            beq         vOp             ; This is an operator
+            cmpa        #'/'            ; Compare A to '/'
+            beq         vOp             ; This is an operator
+            cmpa        #NULL           ; Compare A to NULL character
+            beq         vEndOfLine      ; Check if end of line
+vInvalid    clra                        ; Set A to zero
+            staa        0,X             ; Write Null terminator to X
+            pulx                        ; Restore X from the stack
+            pshx                        ; Save X to the stack
+            jsr         WriteString     ; Write invalid string to serial console
+            ldaa        #CR             ; Load CR into A
+            jsr         putchar         ; Jump to putchar to write the character
+            ldaa        #LF             ; Load LF into A
+            jsr         putchar         ; Jump to putchar to write the character
+            ldx         #invalidStr     ; Load address of invalid string into X
+            jsr         WriteString     ; Write invalid string to serial console
+            ldaa        #4              ; Load 4 into A to set zero bit
+            tap                         ; Transfer A to CCR
+            pulx                        ; Restore X from the stack
+            puld                        ; Restore D from the stack
+            puly                        ; Restore Y from the stack
+            rts                         ; Return to caller
+vOp         staa        operator        ; Store operator in operator buffer
+            ldaa        -2,x            ; Load previous character into A
+            cmpa        #'0'            ; Compare A to '0'
+            blt         vInvalid        ; Invalid string since previous is not number
+            cmpa        #'9'            ; Compare A to '9'
+            bhi         vInvalid        ; Invalid string since previous is not number
+            addb        #1              ; Increment B by 1
+            cmpb        #1              ; Compare B to 1
+            bhi         vInvalid        ; Invalid string since B > 1 and we have another operator
+            ldy         #0              ; Set Y to 0
+            bra         vNumLoop        ; Check for next number
+vEndOfLine  ldaa        -2,x            ; Load previous character into A
+            cmpa        #'0'            ; Compare A to '0'
+            blt         vInvalid        ; Invalid string since previous is not number
+            cmpa        #'9'            ; Compare A to '9'
+            bhi         vInvalid        ; Invalid string since previous is not number
+            ldaa        operator        ; Load operator character from buffer
+            beq         vInvalid        ; If operator buffer is zero, invalid
+            clra                        ; Set A to zero
+            tap                         ; Transfer A to CCR
+            pulx                        ; Restore X from the stack
+            puld                        ; Restore D from the stack
+            puly                        ; Restore Y from the stack
+            rts                         ; Return to caller
+
+;*************************************************************************
+; ReadDecimal subroutine
+;
+; This subroutine will read an ASCII string of a number in decimal and convert it to
+; its value.
+;
+; Input:                   A memory address in register X.
+; Output:                  The value of the number in the Y register, and any errors printed
+;                          to the serial line. Zero bit is set if error occurs.
+; Registers in use:        X for the address of the contents and for a buffer while printing,
+;                          D for multiplication, B for the character, Y for output value.
+; Memory locations in use: Memory Address for serial line, address of the string
+;
+; Comments: This subroutine will return the value in the Y register, and if an error occurs,
+;           the Zero bit in the CCR will be set.
+;
+
+ReadDecimal
+            pshd                        ; Save D to the stack
+            ldy         #0              ; Clear Y register
+dHLoop      ldab        1,x+            ; Read Next character from X
+            beq         dHDone          ; If B == 0, exit loop
+            cmpb        #'+'            ; Compare B to '+'
+            beq         dHDone          ; If B == '+', end of number
+            cmpb        #'-'            ; Compare B to '-'
+            beq         dHDone          ; If B == '-', end of number
+            cmpb        #'*'            ; Compare B to '*'
+            beq         dHDone          ; If B == '+', end of number
+            cmpb        #'/'            ; Compare B to '/'
+            beq         dHDone          ; If B == '-', end of number
+            cmpb        #' '            ; Compare B to space character
+            beq         dHDone          ; If B == ' ', exit loop
+            cmpb        #'0'            ; Compare B to '0' character
+            blt         dHError         ; If B < '0', bad address, exit loop
+            cmpb        #'9'            ; Compare B to '9' character
+            bhi         dHError         ; If B > '9', check if 'A'-'F' characters
+            subb        #'0'            ; Subtract '0' from B to get true value
+            pshb                        ; Save B to the stack
+            ldd         #10             ; load 10 into D
+            emul                        ; Multiply Y and D
+            exg         d,y             ; Transfer data from D to Y
+            pulb                        ; Restore b from the stack
+            aby                         ; Add B to Y
+            bra         dHLoop          ; Branch always to rHLoop
+dHDone      clra                        ; clear A accumulator
+            tap                         ; Transfer A into CCR to clear zero bit
+            puld                        ; Restore D from the stack
+            rts                         ; Return to caller
+dHError     ldaa        #4              ; Load 4 into A to set zero bit in CCR
+            tap                         ; Transfer A into CCR to set zero bit and warn error
+            puld                        ; Restore D from the stack
+            rts                         ; Return to caller
+
+;*************************************************************************
+; strrev subroutine
+;
+; This subroutine will reverse a string from one buffer into another.
+;
+; Input:                   Address of null terminated string in X, address of a large enough
+;                          buffer in Y.
+; Output:                  The string in X reversed in Y.
+; Registers in use:        X for the address of the string, Y for the address of the buffer,
+;                          A to read characters from the string.
+; Memory locations in use: Memory Address for serial line, address of the string & buffer
+;
+; Comments: This subroutine will not check that the output buffer is large enough, that
+;           is the job of the caller.
+;
+
+strrev
+            pshx                        ; Save X to the stack
+            pshy                        ; Save Y to the stack
+            psha                        ; Save A to the stack
+revLoop     ldaa        1,y-            ; Load Character from Y into A, decrement Y
+            beq         revDone         ; If Character is 0, exit loop
+            staa        1,x+            ; Save character in address in X, increment X
+            bra         revLoop         ; Loop back always
+            clra                        ; Set A to Zero
+revDone     staa        1,x+            ; Copy Null terminator into new string
+            pula                        ; Restore A from the stack
+            puly                        ; Restore Y from the stack
+            pulx                        ; Restore X from the stack
+            rts                         ; Return to caller
+
+;*************************************************************************
+; PrintDecimalWord subroutine
+;
+; This subroutine will print a given word of data to the serial in binary.
+;
+; Input:                   1 word of data in register D, Buffer Address in Y
+; Output:                  Decimal representation of the data on the serial console
+; Registers in use:        Y for the address of the buffer, X to count the number of bits
+;                          written and for division, D for the input, A for characters.
+; Memory locations in use: Memory addresses for serial, and operator to hold sign
+;
+; Comments: This subroutine requires serial to be setup and putchar subroutine.
+;
+
+PrintDecimalWord
+            pshx                        ; Save X to the stack
+            pshd                        ; Save D (A:B) to the stack
+            pshy                        ; Save Y to the stack
+            cpd         #0              ; Compare D to zero
+            beq         dIsZero         ; Branch to hIsZero
+            blt         dIsNegative     ; If D < 0, Jump to dIsNegative
+dAfterNeg   psha                        ; Save A to the stack
+            pshy                        ; Save Y to the stack
+            pshx                        ; Save x to the stack
+            ldaa        #'0'            ; Load the '0' character into A
+            ldx         #buffer2        ; Load the address of buffer2 into X
+            ldy         #5              ; Load 5 into Y
+            jsr         memset          ; Write '0' to the first 5 bytes in buffer2
+            pulx                        ; Restore X from the stack
+            puly                        ; Restore Y from the stack
+            clra                        ; Set A to zero
+            staa        0,y             ; Load Zero into Y for Null Terminator
+            pula                        ; Restore A from the stack
+dPrintLoop  ldx         #10             ; Load 10 in X for division
+            idiv                        ; Divide D / 10 to get Hex Digit
+            cpx         #0              ; Compare X to 0
+            beq         dCheck          ; If X == 0, branch to check D is zero
+dDNotZero   addb        #'0'            ; Add '0' to B to get ASCII Character
+            stab        1,+y            ; Save character from B to Y
+            exg         X,D             ; Swap values in X and D
+            bra         dPrintLoop      ; Loop to hPrintLoop
+dCheck      cpd         #0              ; Compare D to 0
+            bne         dDNotZero       ; If D != 0, branch back to hDNotZero
+dPrintDone  ldaa        operator        ; Load operator into A to see if negative
+            cmpa        #'-'            ; Compare A to '-'
+            bne         dNotNeg         ; If A != '-', jump to dNotNeg
+            staa        1,+y            ; Save '-' into buffer
+dNotNeg     ldx         #buffer2        ; Load the address of buffer2 in X
+            jsr         strrev          ; Reverse string in Y in buffer in X
+            jsr         WriteString     ; Jump to write string to write the number
+            ldy         lenBuf2         ; Load the length of buffer2 into Y
+            ldx         #buffer2        ; Load the address of buffer2 into X
+            jsr         Zeros           ; Fill buffer2 with zeros
+            puly                        ; Restore Y from the stack
+            puld                        ; Restore D (A:B) from the stack
+            pulx                        ; Restore X from the stack
+            rts                         ; Return to caller
+dIsZero     ldaa        #'0'            ; Load '0' character into A
+            jsr         putchar         ; Print character to the screen
+            puly                        ; Restore Y from the stack
+            puld                        ; Restore D (A:B) from the stack
+            pulx                        ; Restore X from the stack
+            rts                         ; Return to caller
+dIsNegative psha                        ; Save A to the stack
+            ldaa        #'-'            ; Load '-' into A
+            staa        operator        ; Save '-' to operator buffer
+            pula                        ; Restore A from the stack
+            nega                        ; Two's complement of A
+            suba        #1              ; Subtract 1 from A
+            negb                        ; Two'complement of B
+            subb        #1              ; Subtract 1 from B
+            addd        #1              ; Add 1 to D
+            bra         dAfterNeg       ; Jump back to dAfterNeg
+
+;*************************************************************************
+; Zeros subroutine
+;
+; This subroutine will write zeros to every byte in a given array.
+;
+; Input:                   Address of an array in X and its length in Y
+; Output:                  Zeros in every byte of an array.
+; Registers in use:        X for the address of the array, Y for the length, and A for 0
+; Memory locations in use: Memory Address of the array
+;
+; Comments: This subroutine requires serial to be setup and putchar subroutine.
+;
+
+Zeros
+            psha                        ; Save A to the Stack
+            clra                        ; Clear A
+zerosLoop   staa        1,x+            ; Load A into byte at X
+            dbne        y,zerosLoop     ; Decrement Y and loop if Y != 0
+            pula                        ; Restore A from the stack
+            rts                         ; Return to caller
+
+;*************************************************************************
+; memset subroutine
+;
+; This subroutine will write a given byte to every byte in a given array.
+;
+; Input:                   Address of an array in X and its length in Y, the byte in A
+; Output:                  The given byte in every byte of an array.
+; Registers in use:        X for the address of the array, Y for the length, and A for the given byte
+; Memory locations in use: Memory Address of the array
+;
+; Comments: This subroutine requires serial to be setup and putchar subroutine.
+;
+
+memset
+            staa        1,x+            ; Load A into byte at X
+            dbne        y,memset        ; Decrement Y and loop if Y != 0
+            rts                         ; Return to caller
+
+;*************************************************************************
+; WriteString subroutine
+;
+; This subroutine will write a given null terminated string to the serial.
+;
+; Input:                   Address of null terminated string in X
+; Output:                  Null terminated string written to serial
+; Registers in use:        X for the address of the string and A for the current byte
+; Memory locations in use: Memory Address for serial line, address of the string
+;
+; Comments: This subroutine requires serial to be setup and putchar subroutine.
+;
+
+WriteString
+            psha                        ; Save A to the stack
+writeLoop   ldaa       1,x+             ; Load the byte at addr in X, then add 1
+            beq        doneWrite        ; if A == 0, branch to doneWrite
+            jsr        putchar          ; Jump to putchar to write byte to serial
+            bra        writeLoop        ; branch always to writeLoop
+doneWrite   pula                        ; restore A from the stack
+            rts                         ; return to caller
+
+;*************************************************************************
+; ReadString subroutine
+;
+; This subroutine will read a string from the serial line to a given address.
+;
+; Input:                   Address of an array in X
+; Output:                  Null terminated string in the given array
+; Registers in use:        X for the address of the string Y for the length of the string,
+;                          and A for the current byte
+; Memory locations in use: Memory Address for serial line, address of the string
+;
+; Comments: This subroutine requires serial to be setup and getchar subroutine.
+;
+
+ReadString
+            psha                        ; Save accumulator A to the stack
+            pshy                        ; Save Y to the stack
+            pshx                        ; Save X to the stack
+readLoop    jsr        getchar          ; Jump to putchar to write byte to serial
+            beq        readLoop         ; While A == 0, loop
+            cmpa       #CR              ; If A == CR, exit loop
+            beq        doneRead         ; Branch to doneRead if A == CR
+            staa       1,x+             ; Save the byte to the addr in X, then add 1
+            jsr        putchar          ; Write Character back to the terminal
+            dey                         ; Decrement Y by 1
+            beq        doneRead         ; If Y == 0, no more room, stop reading
+            bra        readLoop         ; branch always to readLoop
+doneRead    ldaa       #LF              ; Load Line Feed into A
+            jsr        putchar          ; Write LF to terminal
+            pulx                        ; Restore X from the stack
+            pulY                        ; Restore Y from the stack
+            pula                        ; restore A from the stack
+            rts                         ; return to caller
+
+;*************************************************************************
+; putchar subroutine
+;
+; This subroutine writes a single byte to a serial line
+;
+; Input:                   A single ASCII byte in accumulator A
+; Output:                  Sends one character to SCI port
+; Registers in use:        Accumulator A with input byte
+; Memory locations in use: SCISR1 and SCIDRL status and data registers
+;
+
+putchar     brclr       SCISR1,#%10000000,putchar   ; wait for transmit buffer empty
+            staa        SCIDRL                      ; send a character
+            rts                                     ; Return to caller
+
+;*************************************************************************
+; putchar subroutine
+;
+; This subroutine reads one byte from the SCI port
+;
+; Input:                   One byte from the SCI port
+; Output:                  One byte in accumulator A
+; Registers in use:        Accumulator A for output byte
+; Memory locations in use: SCISR1 and SCIDRL status and data registers
+;
+
+getchar     brclr       SCISR1,#%00100000,getchar7  ; If no input on SCI port, return 0
+            ldaa        SCIDRL                      ; Read one byte from SCI port into A
+            rts                                     ; Return to caller
+getchar7    clra                                    ; Set A to 0
+            rts                                     ; Return to caller
+
+*
+**************************************************************************
+* Data Section 2: address used [ $3100 to $3FFF ] RAM Memory
+*
+
+invalidStr  dc.b        'Invalid input format',CR,LF,NULL   ; Invalid input error message
+
+prompt      dc.b        'Ecalc> ',NULL                      ; Prompt string for calculator
+
+overflow    dc.b        'Overflow Error',CR,LF,NULL         ; Overflow error message
+
+; msg: this is the main option menu string
+msg         dc.b        'Rules for Calculator:',CR,LF
+            dc.b        '1) Input positive decimal integer numbers only',CR,LF
+            dc.b        '2) Input and output maximum four digit numbers only',CR,LF
+            dc.b        '3) Valid operators are: +, -, *, and /',CR,LF
+            dc.b        '4) Input number with leading zero is OK',CR,LF
+            dc.b        '5) Input only two numbers and one operator in between, no spaces',CR,LF
+            dc.b        '6) In case of an invalid input format, repeat print the user input until the error character',CR,LF
+            dc.b        '7) Keep 16bit internal binary number format, detect and flag overflow error',CR,LF
+            dc.b        '8) Use integer division and truncate any fraction',CR,LF,NULL
+
+            end                         ; last line of the file
diff --git a/cmpen472hw7_McDonnell/Sources/main.asm b/cmpen472hw7_McDonnell/Sources/main.asm
index 9ea49fc..2ea61a0 100644
--- a/cmpen472hw7_McDonnell/Sources/main.asm
+++ b/cmpen472hw7_McDonnell/Sources/main.asm
@@ -6,18 +6,18 @@
 *
 * Revision:     V1.0
 *
-* Date:         Mar. 7, 2025
+* Date:         Mar. 17, 2025
 *
 * Programmer:   Jacob McDonnell
 *
 * Company:      The Pennsylvania State University
 *               Department of Computer Science and Engineering
 *
-* Algorithm:    Simple Serial I/O, address poking and modifying
+* Algorithm:    Simple Serial I/O, ASCII to decimal conversion, & basic math
 *
 * Register Use: A & B to current byte, etc,
 *               X & Y holds address of strings and length of string,
-*               D to hold data and address of the memory location to work on.
+*               D & Y for arithmatic.
 *
 * Memory Use:   RAM Locations from $3000 for data,
 *               RAM Locations from $3100 for program
@@ -588,16 +588,13 @@ overflow    dc.b        'Overflow Error',CR,LF,NULL         ; Overflow error mes
 
 ; msg: this is the main option menu string
 msg         dc.b        'Rules for Calculator:',CR,LF
-            dc.b        '1)  Input positive decimal integer numbers only',CR,LF
-            dc.b        '2)  Input and output maximum four digit numbers only',CR,LF
-            dc.b        '3)  Valid operators are: +, -, *, and /',CR,LF
-            dc.b        '4)  Input number with leading zero is OK',CR,LF
-            dc.b        '5)  Input only two numbers and one operator in between, no spaces',CR,LF
-            dc.b        '6)  Show Ecalc> prompt and echo print user keystrokes unltil Return key',CR,LF
-            dc.b        '7)  Repeat print user input and print answer after the = sign',CR,LF
-            dc.b        '8)  In case of an invalid input format, repeat print the user input until the error character',CR,LF
-            dc.b        '9)  In case of an invalid input format, print error message on the next line: Invalid input format',CR,LF
-            dc.b        '10) Keep 16bit internal binary number format, detect and flag overflow error',CR,LF
-            dc.b        '11) Use integer division and truncate any fraction',CR,LF,NULL
+            dc.b        '1) Input positive decimal integer numbers only',CR,LF
+            dc.b        '2) Input and output maximum four digit numbers only',CR,LF
+            dc.b        '3) Valid operators are: +, -, *, and /',CR,LF
+            dc.b        '4) Input number with leading zero is OK',CR,LF
+            dc.b        '5) Input only two numbers and one operator in between, no spaces',CR,LF
+            dc.b        '6) In case of an invalid input format, repeat print the user input until the error character',CR,LF
+            dc.b        '7) Keep 16bit internal binary number format, detect and flag overflow error',CR,LF
+            dc.b        '8) Use integer division and truncate any fraction',CR,LF,NULL
 
             end                         ; last line of the file
diff --git a/cmpen472hw7_McDonnell/bin/Project.abs b/cmpen472hw7_McDonnell/bin/Project.abs
index 746d865..9c8805a 100644
--- a/cmpen472hw7_McDonnell/bin/Project.abs
+++ b/cmpen472hw7_McDonnell/bin/Project.abs
diff --git a/cmpen472hw7_McDonnell/bin/Project.abs.s19 b/cmpen472hw7_McDonnell/bin/Project.abs.s19
index 898afc6..24a90b5 100644
--- a/cmpen472hw7_McDonnell/bin/Project.abs.s19
+++ b/cmpen472hw7_McDonnell/bin/Project.abs.s19
@@ -21,27 +21,20 @@ S1233300300436FB323D6A300436FB3D36A630270516333720F7323D36353416333E27FB43
 S1233320810D270A6A3016333703270220ED860A1633373031323D4FCC80FC5ACF3D4FCC7F
 S1233340200396CF3D873D496E76616C696420696E70757420666F726D61740D0A00456361
 S1233360616C633E20004F766572666C6F77204572726F720D0A0052756C657320666F72B4
-S12333802043616C63756C61746F723A0D0A31292020496E70757420706F73697469766571
-S12333A020646563696D616C20696E7465676572206E756D62657273206F6E6C790D0A32C5
-S12333C0292020496E70757420616E64206F7574707574206D6178696D756D20666F757252
-S12333E0206469676974206E756D62657273206F6E6C790D0A3329202056616C6964206F68
-S123340070657261746F7273206172653A202B2C202D2C202A2C20616E64202F0D0A34292A
-S12334202020496E707574206E756D6265722077697468206C656164696E67207A65726FDF
-S1233440206973204F4B0D0A35292020496E707574206F6E6C792074776F206E756D62655A
-S1233460727320616E64206F6E65206F70657261746F7220696E206265747765656E2C20D5
-S12334806E6F207370616365730D0A3629202053686F77204563616C633E2070726F6D70D1
-S12334A07420616E64206563686F207072696E742075736572206B65797374726F6B6573E2
-S12334C020756E6C74696C2052657475726E206B65790D0A3729202052657065617420707F
-S12334E072696E74207573657220696E70757420616E64207072696E7420616E737765728C
-S123350020616674657220746865203D207369676E0D0A38292020496E2063617365206F2C
-S12335206620616E20696E76616C696420696E70757420666F726D61742C207265706561D9
-S123354074207072696E7420746865207573657220696E70757420756E74696C2074686569
-S1233560206572726F72206368617261637465720D0A39292020496E2063617365206F660F
-S123358020616E20696E76616C696420696E70757420666F726D61742C207072696E74209F
-S12335A06572726F72206D657373616765206F6E20746865206E657874206C696E653A2079
-S12335C0496E76616C696420696E70757420666F726D61740D0A313029204B656570203190
-S12335E03662697420696E7465726E616C2062696E617279206E756D62657220666F726DB3
-S123360061742C2064657465637420616E6420666C6167206F766572666C6F772065727202
-S12336206F720D0A3131292055736520696E7465676572206469766973696F6E20616E64D0
-S11C3640207472756E6361746520616E79206672616374696F6E0D0A00F2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 S9030000FC
diff --git a/cmpen472hw7_McDonnell/bin/main.dbg b/cmpen472hw7_McDonnell/bin/main.dbg
index 9c0c076..1f12060 100644
--- a/cmpen472hw7_McDonnell/bin/main.dbg
+++ b/cmpen472hw7_McDonnell/bin/main.dbg
@@ -6,18 +6,18 @@
 *
 * Revision:     V1.0
 *
-* Date:         Mar. 7, 2025
+* Date:         Mar. 17, 2025
 *
 * Programmer:   Jacob McDonnell
 *
 * Company:      The Pennsylvania State University
 *               Department of Computer Science and Engineering
 *
-* Algorithm:    Simple Serial I/O, address poking and modifying
+* Algorithm:    Simple Serial I/O, ASCII to decimal conversion, & basic math
 *
 * Register Use: A & B to current byte, etc,
 *               X & Y holds address of strings and length of string,
-*               D to hold data and address of the memory location to work on.
+*               D & Y for arithmatic.
 *
 * Memory Use:   RAM Locations from $3000 for data,
 *               RAM Locations from $3100 for program
@@ -588,15 +588,12 @@ overflow    dc.b        'Overflow Error',CR,LF,NULL         ; Overflow error mes
 
 ; msg: this is the main option menu string
 msg         dc.b        'Rules for Calculator:',CR,LF
-            dc.b        '1)  Input positive decimal integer numbers only',CR,LF
-            dc.b        '2)  Input and output maximum four digit numbers only',CR,LF
-            dc.b        '3)  Valid operators are: +, -, *, and /',CR,LF
-            dc.b        '4)  Input number with leading zero is OK',CR,LF
-            dc.b        '5)  Input only two numbers and one operator in between, no spaces',CR,LF
-            dc.b        '6)  Show Ecalc> prompt and echo print user keystrokes unltil Return key',CR,LF
-            dc.b        '7)  Repeat print user input and print answer after the = sign',CR,LF
-            dc.b        '8)  In case of an invalid input format, repeat print the user input until the error character',CR,LF
-            dc.b        '9)  In case of an invalid input format, print error message on the next line: Invalid input format',CR,LF
-            dc.b        '10) Keep 16bit internal binary number format, detect and flag overflow error',CR,LF
-            dc.b        '11) Use integer division and truncate any fraction',CR,LF,NULL
+            dc.b        '1) Input positive decimal integer numbers only',CR,LF
+            dc.b        '2) Input and output maximum four digit numbers only',CR,LF
+            dc.b        '3) Valid operators are: +, -, *, and /',CR,LF
+            dc.b        '4) Input number with leading zero is OK',CR,LF
+            dc.b        '5) Input only two numbers and one operator in between, no spaces',CR,LF
+            dc.b        '6) In case of an invalid input format, repeat print the user input until the error character',CR,LF
+            dc.b        '7) Keep 16bit internal binary number format, detect and flag overflow error',CR,LF
+            dc.b        '8) Use integer division and truncate any fraction',CR,LF,NULL
 
diff --git a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell.mcp b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell.mcp
index 774ea54..91e58bd 100644
--- a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell.mcp
+++ b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell.mcp
diff --git a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/CWSettingsWindows.stg b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/CWSettingsWindows.stg
index d189836..bb568ef 100644
--- a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/CWSettingsWindows.stg
+++ b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/CWSettingsWindows.stg
diff --git a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/ObjectCode/main.asm.o b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/ObjectCode/main.asm.o
index 746d865..9c8805a 100644
--- a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/ObjectCode/main.asm.o
+++ b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/ObjectCode/main.asm.o
diff --git a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/ObjectCode/main.asm.sx b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/ObjectCode/main.asm.sx
index 9b6629e..c937b8a 100644
--- a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/ObjectCode/main.asm.sx
+++ b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/ObjectCode/main.asm.sx
@@ -21,27 +21,20 @@ S1233300300436FB323D6A300436FB3D36A630270516333720F7323D36353416333E27FB43
 S1233320810D270A6A3016333703270220ED860A1633373031323D4FCC80FC5ACF3D4FCC7F
 S1233340200396CF3D873D496E76616C696420696E70757420666F726D61740D0A00456361
 S1233360616C633E20004F766572666C6F77204572726F720D0A0052756C657320666F72B4
-S12333802043616C63756C61746F723A0D0A31292020496E70757420706F73697469766571
-S12333A020646563696D616C20696E7465676572206E756D62657273206F6E6C790D0A32C5
-S12333C0292020496E70757420616E64206F7574707574206D6178696D756D20666F757252
-S12333E0206469676974206E756D62657273206F6E6C790D0A3329202056616C6964206F68
-S123340070657261746F7273206172653A202B2C202D2C202A2C20616E64202F0D0A34292A
-S12334202020496E707574206E756D6265722077697468206C656164696E67207A65726FDF
-S1233440206973204F4B0D0A35292020496E707574206F6E6C792074776F206E756D62655A
-S1233460727320616E64206F6E65206F70657261746F7220696E206265747765656E2C20D5
-S12334806E6F207370616365730D0A3629202053686F77204563616C633E2070726F6D70D1
-S12334A07420616E64206563686F207072696E742075736572206B65797374726F6B6573E2
-S12334C020756E6C74696C2052657475726E206B65790D0A3729202052657065617420707F
-S12334E072696E74207573657220696E70757420616E64207072696E7420616E737765728C
-S123350020616674657220746865203D207369676E0D0A38292020496E2063617365206F2C
-S12335206620616E20696E76616C696420696E70757420666F726D61742C207265706561D9
-S123354074207072696E7420746865207573657220696E70757420756E74696C2074686569
-S1233560206572726F72206368617261637465720D0A39292020496E2063617365206F660F
-S123358020616E20696E76616C696420696E70757420666F726D61742C207072696E74209F
-S12335A06572726F72206D657373616765206F6E20746865206E657874206C696E653A2079
-S12335C0496E76616C696420696E70757420666F726D61740D0A313029204B656570203190
-S12335E03662697420696E7465726E616C2062696E617279206E756D62657220666F726DB3
-S123360061742C2064657465637420616E6420666C6167206F766572666C6F772065727202
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+S12334A06E70757420666F726D61742C20726570656174207072696E742074686520757315
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+S12334E065720D0A3729204B65657020313662697420696E7465726E616C2062696E617266
+S123350079206E756D62657220666F726D61742C2064657465637420616E6420666C61670A
+S1233520206F766572666C6F77206572726F720D0A38292055736520696E746567657220B6
+S12335406469766973696F6E20616E64207472756E6361746520616E792066726163746928
+S10835606F6E0D0A006E
 S9033100CB
diff --git a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/TargetDataWindows.tdt b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/TargetDataWindows.tdt
index 98fcc7b..a907d06 100644
--- a/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/TargetDataWindows.tdt
+++ b/cmpen472hw7_McDonnell/cmpen472hw7_McDonnell_Data/Standard/TargetDataWindows.tdt