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+**************************************************************************
+* 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
+
+CRGFLG EQU $0037 ; Clock and Reset Generator Flags
+CRGINT EQU $0038 ; Clock and Reset Generator Interrupts
+RTICTL EQU $003B ; Real Time Interrupt Control
+
+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
+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
+
+hours dc.w $0000 ; Buffer to hold the hours of the time
+
+minutes dc.w $0000 ; Buffer to hold the minutes of the time
+
+seconds dc.w $0000 ; Buffer to hold the seconds of the time
+
+counter dc.w $0000 ; Counter for RTI ISR for 1 second
+
+numBuf dc.b $0000 ; Used by ReadDecimal for reading numbers
+
+operator dc.b $0000 ; Used by ReadDecimal for reading numbers
+
+inputBuffer ds.b $0010 ; Input Buffer Length
+
+lenInput dc.w $0010 ; Length of the Input Buffer
+
+outputBuf dc.b 'h' ; Used to control what to output on 7 segment display
+
+n1 dc.b $03
+ dc.b $04
+ dc.b $05
+
+n2 dc.b $06
+ dc.b $07
+ dc.b $08
+
+
+
+*
+**************************************************************************
+* RTI Vector Section: address used [ $FFF0 to $FFF1 ] RAM Memory
+*
+ org $FFF0 ; Memory location for RTI interrupt vector section for simulator
+ dc.w rtiisr ; Real Time Interrupt vector
+*
+**************************************************************************
+* 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 = $0001 => 1.5M baud at 24MHz (for simulation)
+ std SCIBDH ; SCI port baud rate change
+
+ bset RTICTL,%00011001; set RTI: dev=10*(2**10)=2.555msec for C128 board
+ ; 4MHz quartz oscillator clock
+ bset CRGINT,%10000000; enable RTI interrupt
+ bset CRGFLG,%10000000; clear RTI IF (Interrupt Flag)
+
+ ldaa #$FF ; Two 7 segment displays on PORTB
+ staa DDRB ; Set all of PORTB as output
+
+ cli
+
+mainLoop
+ ldaa #3
+ psha
+
+ ldaa #4
+ psha
+
+ ldaa #5
+ psha
+
+ ldd #0
+ jsr SORT
+
+ pula
+ pula
+ pula
+
+ jsr add3
+
+ ldaa #200
+ clrb
+loopy incb
+ suba #$01
+ ble loopy
+
+ ldaa #$65
+ ldab #$43
+ ldx #256
+ idiv
+ tba
+ jsr putchar
+ xgdx
+ tba
+ jsr putchar
+
+ bra mainLoop ; Loop back to mainLoop always
+
+**************************************************************************
+* Subroutine Section: address used [ $3100 to $3FFF ] RAM Memory
+*
+
+SORT
+ pshb
+ ldab 3,sp
+ cmpb 4,sp
+ bls skip
+ movb 4,sp,3,sp
+ stab 4,sp
+skip ldab 4,sp
+ cmpb 5,sp
+ bls done
+ movb 5,sp,4,sp
+ stab 5,sp
+ ldab 3,sp
+ cmpb 4,sp
+ bls done
+ movb 4,sp,3,sp
+ stab 4,sp
+done pulb
+ rts
+
+add3
+ pshx
+ pshy
+ pshd
+ ldx #n1
+ ldy #n2
+ inx
+ inx
+ iny
+ iny
+ ldab #4
+aloop dbeq b,adone
+ ldaa 0,x
+ adca 1,y-
+ staa 1,x-
+ bra aloop
+adone puld
+ puly
+ pulx
+ rts
+
+;*************************************************************************
+; rtiisr subroutine
+;
+; This subroutine will increment the counter, seconds, minutes, & hours counters
+; to track the time. This subroutine will be called ~400 times a second.
+;
+; Input: No input other than the timer to call the isr.
+; Output: The counter, seconds, minutes, & hours buffers will
+; be updated to track the time, the time & prompt will be
+; printed every second.
+; Registers in use: X for adding to the counter, seconds, minutes, & hours buffers.
+; Memory locations in use: Memory Address for serial line, Memory addresses for RTIISR control,
+; Buffer words for counters, seconds, minutes, & hours buffers.
+;
+; Comments: The counter buffer should be compared to 400, but for the simulator,
+; the counter is compared to 200 to better simulate 1 second on my computer.
+;
+
+rtiisr bset CRGFLG,%10000000; Clear RTI Interrupt Flag
+ ldx counter
+ inx
+ stx counter
+ cpx #100
+ bne rtiSkip
+ ldx #0
+ stx counter
+ ldaa PORTB
+ eora #%00010000
+ staa PORTB
+rtiSkip RTI ; Return from RTI ISR
+
+;*************************************************************************
+; PrintTime subroutine
+;
+; This subroutine will print the time, command prompt, and maybe an error prompt.
+;
+; Input: No input.
+; Output: The time prompt, time, command prompt, the current input,
+; and/or an error on the serial console.
+; Registers in use: A for the characters to print, X for buffer addresses,
+; Y for buffer lengths, D for the seconds/minutes/hours for calling TimeOnPortB
+; Memory locations in use: Memory Address for serial line, Buffer words for counters,
+; seconds, minutes, & hours buffers, and buffer to print time,
+; outputBuf for tracking what to output on PORTB.
+;
+; Comments: This subroutine requires TimeOnPortB subroutine and to be setup. The subroutine
+; will print the current user input if its not finished.
+;
+
+PrintTime
+ pshd ; Save D to the stack
+ pshy ; Save Y to the stack
+ pshx ; Save X to the stack
+ ldaa #CR ; Load the character CR into A
+ jsr putchar ; Write the character to the serial
+ ldaa #LF ; Load the character LF into A
+ jsr putchar ; Write the character to the serial
+ ldx #clock ; Load the address of the clock prompt into X
+ jsr WriteString ; Write the string to serial
+ ldd hours ; Load the hours into D
+ cpd #10 ; Compare D to 10
+ bhs goodHours ; If D >= goodHours
+ psha ; Save A to the stack
+ ldaa #'0' ; Load '0' character into A
+ jsr putchar ; Print '0' to the serial
+ pula ; Restore A from the stack
+goodHours ldy #buffer ; Load the address of buffer into Y
+ jsr PrintDecimalWord; Print the number to the serial
+ ldaa #':' ; Load the character ':' into A
+ jsr putchar ; Write the character to the serial
+ ldd minutes ; Load the minutes into D
+ cpd #10 ; Compare D to 10
+ bhs goodMins ; If D >= goodMins
+ psha ; Save A to the stack
+ ldaa #'0' ; Load '0' character into A
+ jsr putchar ; Print '0' to the serial
+ pula ; Restore A from the stack
+goodMins ldy #buffer ; Load the address of buffer into Y
+ jsr PrintDecimalWord; Print the number to the serial
+ ldaa #':' ; Load the character ':' into A
+ jsr putchar ; Write the character to the serial
+ ldd seconds ; Load the seconds into D
+ cpd #10 ; Compare D to 10
+ bhs goodSecs ; If D >= goodSecs
+ psha ; Save A to the stack
+ ldaa #'0' ; Load '0' character into A
+ jsr putchar ; Print '0' to the serial
+ pula ; Restore A from the stack
+goodSecs ldy #buffer ; Load the address of buffer into Y
+ jsr PrintDecimalWord; Print the number to the serial
+ ldaa #' ' ; Load ' ' character into A
+ jsr putchar ; Write the character to the serial console
+ jsr putchar ; Write the character to the serial console
+ jsr putchar ; Write the character to the serial console
+ jsr putchar ; Write the character to the serial console
+ ldx #CMD ; Load the address of CMD into X
+ jsr WriteString ; Write the string to the serial
+ ldx #inputBuffer ; Load the address of the inputBuffer into X
+ jsr WriteString ; Write the string to the serial
+ ldaa outputBuf ; Load outputBuf into A
+ cmpa #'h' ; Compare A to 'h'
+ bne pTimeIsM ; If A != 'h', branch to pTimeIsM
+ ldd hours ; Load hours into B
+ bra skipRest ; Jump to skipRest
+pTimeIsM cmpa #'m' ; Compare A to 'm'
+ bne pTimeIsS ; If A != 'm', branch to pTimeIsS
+ ldd minutes ; Load Minutes into D
+ bra skipRest ; Jump to skipRest
+pTimeIsS ldd seconds ; Load seconds into D
+skipRest jsr TimeOnPortB ; Call TimeOnPortB to output time
+ pulx ; Restore X from the stack
+ puly ; Restore Y from the stack
+ puld ; Restore D from the stack
+ rts ; Return to caller
+
+;*************************************************************************
+; TimeOnPortB subroutine
+;
+; This subroutine will output the time given on on PORTB for two seven segment displays.
+;
+; Input: Two Digit Decimal number in register D.
+; Output: The given two digit decimal number on PORTB for two 7 segment displays.
+; Registers in use: D for the input, and for math to split the digits, X for math to split digits.
+; Memory locations in use: PORTB memory location.
+;
+; Comments: This subroutine will only work with two digit decimal numbers, and one digit decimal
+; numbers (leading zeros will be added).
+;
+
+TimeOnPortB
+ pshd ; Save D to the stack
+ pshx ; Save X to the stack
+ ldx #10 ; Load 10 into X to get digit
+ idiv ; Divide D by X and save Digit into D
+ pshb ; Save B to the stack (Lower Byte of D)
+ exg x,d ; Swap X and D
+ ldx #10 ; Load 10 into X to get digit
+ lslb ; Shift B left by 1
+ lslb ; Shift B left by 1
+ lslb ; Shift B left by 1
+ lslb ; Shift B left by 1
+ orab 1,sp+ ; Or B with Digit on stack
+ stab PORTB ; Save B to PORTB
+ pulx ; Restore X from the stack
+ puld ; Restore D from the stack
+ rts ; Return from 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 ':'
+ 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
+ pshy ; Save Y to the stack
+ pshd ; Save D (A:B) 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
+ puld ; Restore D (A:B) from the stack
+ puly ; Restore Y 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
+ puld ; Restore D (A:B) from the stack
+ puly ; Restore Y 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 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
+*
+
+clock dc.b 'Clock> ',NULL ; Prompt string for clock
+
+CMD dc.b 'CMD> ',NULL ; Prompt string for CMD
+
+error dc.b 'Error> ',NULL ; Prompt string for errors
+
+badInput dc.b 'Invalid Input',NULL ; Invalid Input Prompt
+
+; twMsg: welcome message for typewrite
+twMsg dc.b CR,LF,'Clock stopped and Typewrite program started.',CR,LF
+ dc.b 'You may type below.',CR,LF,NULL
+
+; msg: this is the main option menu string
+msg dc.b 'Commands:',CR,LF
+ dc.b 't: Set the time in format HH:MM:SS',CR,LF
+ dc.b 'h: Display the hours on the 7 segment displays',CR,LF
+ dc.b 'm: Display the minutes on the 7 segment displays',CR,LF
+ dc.b 's: Display the seconds on the 7 segment displays',CR,LF
+ dc.b 'q: Stop the clock and enter typewriter',CR,LF,NULL
+
+ end ; last line of the file
generated by cgit v1.2.3 (git 2.46.0) at 2026-05-15 13:37:34 +0000