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|
**************************************************************************
*
* 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
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