.INCLUDE "m128def.inc"
;==========================================================STUDENT DIRECTIVES====================================================
.equ addresLineOne = 0x0100
.equ addresLineTwo = 0x0200
;===================================================================MACROS==========================================================================

;Macro operations to increase the readibility of the code and avoid repetition
;This is an operation for initializing Z register with an address where the data for LCD_Line_One is coming from
.MACRO initZforLineOne
    ldi ZH, high(addresLineOne)
    ldi ZL, low(addresLineOne)
.ENDMACRO
;This is an operation for initializing Z register with an address where the data for LCD_Line_Two is coming from
.MACRO initZforLineTwo
    ldi ZH, high(addresLineTwo)
    ldi ZL, low(addresLineTwo)
.ENDMACRO
;This is an operation for storing giving register values in binary by using ascii code of one and zero so that LCD can print data in the right format
;It also includes a null character at the end of the string to ensure that printing operation will terminate
.MACRO storeRegisterForLCD
    ;convert the number to ascii and store in address text
    ldi r17, '1'
    sbrs @0, 7
    ldi r17, '0'
    st Z+, r17
    ldi r17, '1'
    sbrs @0, 6
    ldi r17, '0'
    st Z+, r17
    ldi r17, '1'
    sbrs @0, 5
    ldi r17, '0'
    st Z+, r17
    ldi r17, '1'
    sbrs @0, 4
    ldi r17, '0'
    st Z+, r17
    ldi r17, '1'
    sbrs @0, 3
    ldi r17, '0'
    st Z+, r17
    ldi r17, '1'
    sbrs @0, 2
    ldi r17, '0'
    st Z+, r17
    ldi r17, '1'
    sbrs @0, 1
    ldi r17, '0'
    st Z+, r17
    ldi r17, '1'
    sbrs @0, 0
    ldi r17, '0'
    st Z+, r17
    call nullToZLast
.ENDMACRO
;This is an operation for calculating the parity bit of first number which is coming from PIND.
;It also appends the calculated parity bit to the memory adress stored in Z register and adds null character next to it for terminating printing operation to LCD
.MACRO contParitywithStore
    sbic pind, 0
    inc @0
    sbic pind, 1
    inc @0
    sbic pind, 2
    inc @0
    sbic pind, 3
    inc @0
    sbic pind, 4
    inc @0
    sbic pind, 5
    inc @0
    sbic pind, 6
    inc @0
    sbic pind, 7
    inc @0

    ldi r17, '0'
    SBRC @0, 0
    ldi r17, '1'
    st Z+, r17
    call nullToZLast
.ENDMACRO
;=============================================================LCD DIRECTIVES===================================================
;Majority of the directives come from LCD inferface yet there are two in the beginning of to code for address stored in Z register
.equ fclk = 8000000 ; system clock frequency (for delays)
; register usage
.def temp = R16 ; temporary storage
; LCD interface
.equ lcd_D7_port = PORTC ; lcd D7 connection
.equ lcd_D7_bit = PORTC7
.equ lcd_D7_ddr = DDRC
.equ lcd_D6_port = PORTC ; lcd D6 connection
.equ lcd_D6_bit = PORTC6
.equ lcd_D6_ddr = DDRC
.equ lcd_D5_port = PORTC ; lcd D5 connection
.equ lcd_D5_bit = PORTC5
.equ lcd_D5_ddr = DDRC
.equ lcd_D4_port = PORTC ; lcd D4 connection
.equ lcd_D4_bit = PORTC4
.equ lcd_D4_ddr = DDRC
.equ lcd_E_port = PORTB ; lcd Enable pin
.equ lcd_E_bit = PORTB5
.equ lcd_E_ddr = DDRB
.equ lcd_RS_port = PORTB ; lcd Register Select pin
.equ lcd_RS_bit = PORTB2
.equ lcd_RS_ddr = DDRB
; LCD module Lines
.equ lcd_LineOne = 0x00 ; line 1
.equ lcd_LineTwo = 0x40 ; line 2
; LCD Defined instructions
.equ lcd_Clear = 0b00000001 ; ASCII 'space' for all characters
.equ lcd_Home = 0b00000010 ; first position on first line
.equ lcd_EntryMode = 0b00000110 ; shift cursor from left to right on read/write
.equ lcd_DisplayOff = 0b00001000 ; turn display off
.equ lcd_DisplayOn = 0b00001100 ; display on, cursor off, don't blink character
.equ lcd_FunctionReset = 0b00110000 ; reset the LCD
.equ lcd_FunctionSet4bit = 0b00101000 ; 4-bit data, 2-line display, 5 x 7 font
.equ lcd_SetCursor = 0b10000000 ; set cursor position

; ****************************** Reset Vector *******************************
.org 0x0000
 jmp start ; jump over Interrupt Vectors, Program ID etc.
;******************************* Program ID *********************************
.org INT_VECTORS_SIZE
; ****************************** Main Program Code **************************
start:
; initialize the stack pointer to the highest RAM address
 ldi temp,low(RAMEND)
 out SPL,temp
 ldi temp,high(RAMEND)
 out SPH,temp
; configure the microprocessor pins for the data lines
 sbi lcd_D7_ddr, lcd_D7_bit ; 4 data lines - output
 sbi lcd_D6_ddr, lcd_D6_bit
 sbi lcd_D5_ddr, lcd_D5_bit
 sbi lcd_D4_ddr, lcd_D4_bit
; configure the microprocessor pins for the control lines
 sbi lcd_E_ddr, lcd_E_bit ; E line - output
 sbi lcd_RS_ddr, lcd_RS_bit ; RS line - output
; initialize the LCD controller
 call lcd_init_4d ; initialize the LCD display for a 4-bit interface

 ldi r20, 0x00
 out ddra, r20
 out ddrd, r20
 out ddre, r20
 jmp READ

READ: ;start of each capture iteration
    call clearLcdMemoryAddresses
    in r20, pind
    in r17, pine
    in R21, pina
    andi R21,0x03
    CPI R21,0x00
    BREQ PROCESS_ZERO
    CPI R21,0x01
    BREQ PROCESS_ONE
    CPI R21,0x10
    BREQ PROCESS_TWO
    CPI R21,0x11
    BREQ PROCESS_THREE

PROCESS_ZERO:
    CALL mode00
    jmp printToLCD
    JMP READ
PROCESS_ONE:
    CALL mode01
    jmp printToLCD
    JMP READ
PROCESS_TWO:
    ;CALL mode00
    JMP READ
PROCESS_THREE:
    ;CALL mode00
    JMP READ

mode01: ;print first number and an even parity bit
    initZforLineOne
    storeRegisterForLCD r20

    ldi r18, 0; some odd number
    contParitywithStore r18
    call nullToZLast

    jmp printToLcd

mode00: ;print first number and an odd parity bit
    initZforLineOne
    storeRegisterForLCD r20

    ldi r18, 1;some even number
    contParitywithStore r18
    call nullToZLast

    jmp printToLcd
mode11:
    mov r18, r17
    sub r17, r20
    brmi logicisfalse
    mov r18, r17
    call printHex
    initZforLineOne
    storeRegisterForLCD r18
    jmp printToLcd
    logicisfalse:
        sub r20, r18
        mov r18, r20
        call printHex
        initZforLineOne
        storeRegisterForLCD r18
        jmp printToLcd

mode10:
    mov r18, r17
    sub r18, r20
    breq equal
    mov r18, r17
    sub r18, r20
    brmi less
        mov r18, r17
        call printHex
        jmp printToLcd
    equal:
        initZforLineTwo
        ldi r19, 'E'
        st Z+, r19
        ldi r19, 'Q'
        st Z+, r19
        jmp printToLcd
    less:
        mov r18, r20
        call printHex
        jmp printToLcd

;====================================================================STUDENT WRITTEN FUNCTIONS====================================================
printHex:
    initZforLineTwo
    mov r19, r18
    swap r19
    andi r19, 0x0F
    cpi r19, 0x0A
    brlt lessThanAR
    subi r19, 9
    ori r19, 0x40
    st Z+, r19
    jmp secondHex
    lessThanAR:
    ori r19,0x30
    st Z+, r19
    secondHex:
    mov r19, r18
    andi r19, 0x0F
    cpi r19, 0x0A
    brlt lessThanAL
    subi r19, 9
    ori r19, 0x40
    st Z+, r19
    ret
    lessThanAL:
    ori r19,0x30
    st Z+, r19
    ret



printToLcd:
in R16, PINB;
; display the first line of information
 ldi ZH, high(addresLineOne) ; point to the information that is to be displayed
 ldi ZL, low(addresLineOne)
ldi temp, lcd_LineOne ; point to where the information should be displayed
call lcd_write_string_4d
; display the second line of information
 ldi ZH, high(addresLineTwo) ; point to the information that is to be displayed
 ldi ZL, low(addresLineTwo)
ldi temp, lcd_LineTwo ; point to where the information should be displayed
call lcd_write_string_4d

rjmp READ
 nullToZLast:
    ldi r17, 0x00
    st Z, r17
    ret

fillZWithEmptySpaces:
    ldi r17, lcd_Clear
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    st Z+, r17
    call nullToZLast
    ret

clearLcdMemoryAddresses:
    initZforLineOne
    call fillZWithEmptySpaces

    initZforLineTwo
    call fillZWithEmptySpaces
    ret
; ****************************** End of Main Program Code *******************




; ****************************** LCD Code **************************
initializeLCD:
; initialize the stack pointer to the highest RAM address
    ldi temp,low(RAMEND)
    out SPL,temp
    ldi temp,high(RAMEND)
    out SPH,temp

; configure the microprocessor pins for the data lines
    sbi lcd_D7_ddr, lcd_D7_bit ; 4 data lines - output
    sbi lcd_D6_ddr, lcd_D6_bit
    sbi lcd_D5_ddr, lcd_D5_bit
    sbi lcd_D4_ddr, lcd_D4_bit

; configure the microprocessor pins for the control lines
    sbi lcd_E_ddr, lcd_E_bit ; E line - output
    sbi lcd_RS_ddr, lcd_RS_bit ; RS line - output

; initialize the LCD controller
    call lcd_init_4d ; initialize the LCD display for a 4-bit interface

    jmp start



; ============================== 4-bit LCD Function Calls ======================
; Name: lcd_init_4d -- initialize the LCD module for a 4-bit data interface

lcd_init_4d:
; Power-up delay
    ldi temp, 100 ; initial 40 mSec delay
    call delayTx1mS

; IMPORTANT - At this point the LCD module is in the 8-bit mode and it is expecting to receive
; 8 bits of data, one bit on each of its 8 data lines, each time the 'E' line is pulsed.
;
; Since the LCD module is wired for the 4-bit mode, only the upper four data lines are connected to
; the microprocessor and the lower four data lines are typically left open. Therefore, when
; the 'E' line is pulsed, the LCD controller will read whatever data has been set up on the upper
; four data lines and the lower four data lines will be high (due to internal pull-up circuitry).
;
; Fortunately the 'FunctionReset' instruction does not care about what is on the lower four bits so
; this instruction can be sent on just the four available data lines and it will be interpreted
; properly by the LCD controller. The 'lcd_write_4' subroutine will accomplish this if the
; control lines have previously been configured properly.

; Set up the RS and E lines for the 'lcd_write_4' subroutine.
    cbi lcd_RS_port, lcd_RS_bit ; select the Instruction Register (RS low)
    cbi lcd_E_port, lcd_E_bit ; make sure E is initially low

; Reset the LCD controller.
    ldi temp, lcd_FunctionReset ; first part of reset sequence
    call lcd_write_4
    ldi temp, 10 ; 4.1 mS delay (min)
    call delayTx1mS

    ldi temp, lcd_FunctionReset ; second part of reset sequence
    call lcd_write_4
    ldi temp, 200 ; 100 uS delay (min)
    call delayTx1uS

    ldi temp, lcd_FunctionReset ; third part of reset sequence
    call lcd_write_4
    ldi temp, 200 ; this delay is omitted in the data sheet call
    call delayTx1uS

; Preliminary Function Set instruction - used only to set the 4-bit mode.
; The number of lines or the font cannot be set at this time since the controller is still in the
; 8-bit mode, but the data transfer mode can be changed since this parameter is determined by one
; of the upper four bits of the instruction.

    ldi temp, lcd_FunctionSet4bit ; set 4-bit mode
    call lcd_write_4
    ldi temp, 80 ; 40 uS delay (min)
    call delayTx1uS

; Function Set instruction
    ldi temp, lcd_FunctionSet4bit ; set mode, lines, and font
    call lcd_write_instruction_4d
    ldi temp, 80 ; 40 uS delay (min)
    call delayTx1uS

; The next three instructions are specified in the data sheet as part of the initialization routine,
; so it is a good idea (but probably not necessary) to do them just as specified and then redo them
; later if the application requires a different configuration.

; Display On/Off Control instruction
    ldi temp, lcd_DisplayOff ; turn display OFF
    call lcd_write_instruction_4d
    ldi temp, 80 ; 40 uS delay (min)
    call delayTx1uS

; Clear Display instruction
    ldi temp, lcd_Clear ; clear display RAM
    call lcd_write_instruction_4d
    ldi temp, 4 ; 1.64 mS delay (min)
    call delayTx1mS

; Entry Mode Set instruction
    ldi temp, lcd_EntryMode ; set desired shift characteristics
    call lcd_write_instruction_4d
    ldi temp, 80 ; 40 uS delay (min)
    call delayTx1uS

; This is the end of the LCD controller initialization as specified in the data sheet, but the display
; has been left in the OFF condition. This is a good time to turn the display back ON.

; Display On/Off Control instruction
    ldi temp, lcd_DisplayOn ; turn the display ON
    call lcd_write_instruction_4d
    ldi temp, 80 ; 40 uS delay (min)
    call delayTx1uS
    ret

; ---------------------------------------------------------------------------
; Name: lcd_write_string_4d ; Purpose: display a string of characters on the LCD
; Entry: ZH and ZL pointing to the start of the string
; (temp) contains the desired DDRAM address at which to start the display
; Exit: no parameters
; Notes: the string must end with a null (0)
; uses time delays instead of checking the busy flag

lcd_write_string_4d:
; preserve registers
    push ZH ; preserve pointer registers
    push ZL

; set up the initial DDRAM address
    ori temp, lcd_SetCursor ; convert the plain address to a set cursor instruction
    call lcd_write_instruction_4d ; set up the first DDRAM address
    ldi temp, 80
    call delayTx1uS

; write the string of characters
lcd_write_string_4d_01:
    ld temp, Z+ ; get a character
    cpi temp, 0 ; check for end of string
    breq lcd_write_string_4d_02 ; done

; arrive here if this is a valid character
    call lcd_write_character_4d ; display the character
    ldi temp, 80
    call delayTx1uS
    rjmp lcd_write_string_4d_01 ; not done, send another character

; arrive here when all characters in the message have been sent to the LCD module
lcd_write_string_4d_02:
    pop ZL ; restore pointer registers
    pop ZH
    ret

; ---------------------------------------------------------------------------
; Name: lcd_write_character_4d
; Purpose: send a byte of information to the LCD data register
; Entry: (temp) contains the data byte ; Exit: no parameters
; Notes: does not deal with RW (busy flag is not implemented)

lcd_write_character_4d:
    sbi lcd_RS_port, lcd_RS_bit ; select the Data Register (RS high)
    cbi lcd_E_port, lcd_E_bit ; make sure E is initially low
    call lcd_write_4 ; write the upper 4-bits of the data
    swap temp ; swap high and low nibbles
    call lcd_write_4 ; write the lower 4-bits of the data
    ret

; ---------------------------------------------------------------------------
; Name: lcd_write_instruction_4d -- Send a byte of information to the LCD instruction register
lcd_write_instruction_4d:
    cbi lcd_RS_port, lcd_RS_bit ; select the Instruction Register (RS low)
    cbi lcd_E_port, lcd_E_bit ; make sure E is initially low
    call lcd_write_4 ; write the upper 4-bits of the instruction
    swap temp ; swap high and low nibbles
    call lcd_write_4 ; write the lower 4-bits of the instruction
    ret

; ---------------------------------------------------------------------------
; Name: lcd_write_4 Send 4-bits of information to the LCD module
; Entry: (temp) contains a byte of data with the desired 4-bits in the upper nibble
; (RS) is configured for the desired LCD register
; (E) is low
; (RW) is low
lcd_write_4:
; set up D7
    sbi lcd_D7_port, lcd_D7_bit ; assume that the D7 data is '1'
    sbrs temp, 7 ; check the actual data value
    cbi lcd_D7_port, lcd_D7_bit ; arrive here only if the data was actually '0'

; set up D6
    sbi lcd_D6_port, lcd_D6_bit ; repeat for each data bit
    sbrs temp, 6
    cbi lcd_D6_port, lcd_D6_bit

; set up D5
    sbi lcd_D5_port, lcd_D5_bit
    sbrs temp, 5
    cbi lcd_D5_port, lcd_D5_bit

; set up D4
    sbi lcd_D4_port, lcd_D4_bit
    sbrs temp, 4
    cbi lcd_D4_port, lcd_D4_bit

; write the data
; 'Address set-up time' (40 nS)
    sbi lcd_E_port, lcd_E_bit ; Enable pin high
    call delay1uS ; implement 'Data set-up time' (80 nS) and 'Enable pulse width' (230 nS)
    cbi lcd_E_port, lcd_E_bit ; Enable pin low
    call delay1uS ; implement 'Data hold time' (10 nS) and 'Enable cycle time' (500 nS)
    ret

; ============================== End of 4-bit LCD Subroutines ===============

; ============================== Time Delay Subroutines =====================
; Name: delayYx1mS Delay of (YH:YL) x 1 mS

delayYx1mS:
    call delay1mS ; delay for 1 mS
    sbiw YH:YL, 1 ; update the the delay counter
    brne delayYx1mS ; counter is not zero

; arrive here when delay counter is zero (total delay period is finished)
    ret

; ---------------------------------------------------------------------------
; Name: delayTx1mS Provide a delay of (temp) x 1 mS
delayTx1mS:
    call delay1mS ; delay for 1 mS
    dec temp ; update the delay counter
    brne delayTx1mS ; counter is not zero

; arrive here when delay counter is zero (total delay period is finished)
    ret

; ---------------------------------------------------------------------------
; Name: delay1mS -- Delay of 1 mS
delay1mS:
    push YL ; [2] preserve registers
    push YH ; [2]
    ldi YL, low (((fclk/1000)-18)/4) ; [1] delay counter
    ldi YH, high(((fclk/1000)-18)/4) ; [1]

delay1mS_01:
    sbiw YH:YL, 1 ; [2] update the the delay counter
    brne delay1mS_01 ; [2] delay counter is not zero
; arrive here when delay counter is zero
    pop YH ; [2] restore registers
    pop YL ; [2]
    ret
; ---------------------------------------------------------------------------
; Name: delayTx1uS Delay of (temp) x 1 uS with a 8 MHz clock frequency
delayTx1uS:
    call delay1uS ; delay for 1 uS
    dec temp ; decrement the delay counter
    brne delayTx1uS ; counter is not zero
; arrive here when delay counter is zero (total delay period is finished)
    ret
; ---------------------------------------------------------------------------
; Name: delay1uS
; Purpose: Delay of 1 uS with a 8 MHz clock frequency
delay1uS:
    push temp ; [2] Consume clock cycles
    pop temp ; [2]
    ret
; ============================== End of Time Delay Subroutines ==============