;Julie Hui
;2/8/11
;6.115 Leeb
;Lab 1 Ex.6

;supposed to:
;makes a simple calculator using the keypad
;adds/subtracts two 3-digit numbers and displays the sum

;instead does this:
;takes and displayes two 3-digit number from keypad
;gets and displays +/- on screen
;gives out 099 as answer for anything...


org 00h                             ;power up and reset vector
    ljmp start                      ;when the micro wakes up, jump to the beginning
                                    ;of the main body or loop in the program, called "start"
org 100h                            ;Start the serial port by calling subroutine "init"
start:
    lcall init                      ;Start the serial port by calling subroutine "init".
    clr P3.2                        ;set Output enable on low
    loop:
        lcall storenums             ;store the ASCII code for each key into R5
        lcall createnums            ;creates the two numbers input from the keypad
        lcall addorsub              ;waits for +/- and runs getsum or getsub
        lcall displaysum            ;displays sum on monitor
    sjmp loop

init:
;set up serial port with a 11.0592 MHz crystal,
;use timer 1 for 9600 baud serial communications
    mov tmod, #00100000b            ;set timer 1 for auto reload-mode 2
    mov tcon, #01000000b            ;run counter 1
    mov th1, #0fdh                  ;set 9600 baud with xtal=11.059mhz
    mov scon, #01010000b            ;set serial control reg for 8 bit data and mode 1
    ret

getnum:
;this routine "gets" or receives a character from the PC, transmitted over
;the serial port. RI is the same as SCON.0 - the assembler recognizes
;either shorthand. The 7-bit ASCII code is returned in the accumulator.
;STORES THE ASCII CODE FROM KEYPAD INTO ACC
    jnb P3.3, getnum                ;wait till character received
    pop DPH                         ;pop getnum address out of stack
    pop DPL
    mov a, P1                       ;move byte from P1 into acc
    anl a, #0fh                     ;mask off 5th, 6th, 7th, 8th bit
    loop1:                          ;only get digit once
        jb P3.3,loop1
    push DPL                            ;pop getnum address back to stack
    push DPH
    ret

getkey:
;gets the correct value of the key and stores it in ACC
    pop DPH                         ;pop getkey address out of stack
    pop DPL
    push DPL                        ;pop getnum address back to stack
    push DPH
    inc a                           ;increase a by 1 byte
    inc a                           ;increase a by 1 byte
    movc a,@a+pc                    ;gets correct keypad ASCII value for each key
    mov R5,a                        ;STORES CORRECT ASCII KEY VALUE INTO R5
    ret
    db 31h, 32h, 33h, 2Bh, 34h, 35h, 36h, 2Dh, 37h, 38h, 39h, 43h, 2Ah, 30h, 23h, 44h

sndnum:
;this routine "sends" or transmits a number to the PC, using the serial
;port. The character to be sent is stored in the accumulator. SCON.1 and
;TI are the same as far as the assembler is concerned
;saves the ASCII code for the key in a and sbuf
    pop DPH                         ;pop sndnum address out of stack
    pop DPL
    clr scon.1                      ;clear the ti complete flag
    mov sbuf,R5                     ;move a number from R5 to the sbuf, ASCII KEY VALUE STORED IN SBUF AND R5
    txloop:
        jnb scon.1, txloop          ;wait till chr is sent
    push DPL                            ;pop sndnum address back to stack
    push DPH
    ret

sndchr1:
;this routine "sends" or transmits a character to the PC, using the serial
;port. The character to be sent is stored in the accumulator. SCON.1 and
;TI are the same as far as the assembler is concerned
    clr scon.1                  ;clear the ti complete flag.
txloop1:
    jnb scon.1, txloop1         ;wait till chr is sent
    ret

crlf:
;carraige return and linefeed
    mov sbuf, #00h
    mov sbuf, #0Ah              ;moves the ASCII value 10 into sbuf causing a linefeed operation
    lcall sndchr1
    mov sbuf, #0Dh
    lcall sndchr1
    ret

storenums:
;moves each digit typed on the keyboard to the stack
    pop ACC                         ;pops storenums address out of stack using ACC
    mov R4,A                        ;stores part of adress in R4
    clr A
    pop ACC
    mov R3, A                       ;stores part of address in R3
    clr A

    mov R2,#03h                     ;moves the value of 3 into R2
    loopsn1:                        ;gets first 3 digit number from keypad then exits
        lcall getnum                ;gets digit from keyboard
        lcall getkey                ;gets correct AsCII code for key
        lcall sndnum                ;send digit back to monitor
        clr A
        mov A,sbuf                  ;moves correct ASCII key code in sbuf to ACC
        mov R1,#30h                 ;moves 48 into R1
        subb A,R1                   ;subtracts 48 from the ASCII code to get the real digit value and stores sum in A
        mov R1,#00h                 ;clear R1
        push ACC                    ;push real value of input digit into stack
        djnz R2,loopsn1             ;reduced value of R2 by 1. when R2 is 0, exits loop

    lcall crlf


    mov R2,#00h                     ;clear R2
    mov R2,#03h                     ;move the value 2 into R2
    loopsn2:                        ;gets second 3 digit number from keypad then exits
        lcall getnum                ;gets digit from keyboard
        lcall getkey                ;gets correct AsCII code for key
        lcall sndnum                ;send digit back to monitor
        clr A                       ;clears A
        mov A,sbuf                  ;moves key ASCII value from sbut into A
        mov R1,#30h                 ;moves 48 into R1
        subb A,R1                   ;subtracts 48 from the ASCII code of digit to get real digit value
        mov R1,#00h                 ;clear R1
        push ACC                    ;push key real value of input digit into stack
        djnz R2,loopsn2             ;reduces R2 value by 1. When R2=0, exits loop

    lcall crlf

    mov A,R3                        ;pops subroutine addresses back into stack
    push ACC
    mov A,R4
    push ACC
    ret

createnums:
;create the two 3-digit numbers and store each in a byte in the memory
    ;second number entered
    pop DPH
    pop DPL

    clr ACC
    pop ACC
    mov R2,#00h
    mov R2,A            ;gets second 1x-digit from stack and store in R2

    pop ACC             ;gets second 10xdigit and store in ACC
    mov B,#0Ah          ;moves value of 10 into B
    mul AB              ;multiply second 10x digit by 10 and stores in A
    add A,R2            ;add second 10 digit to second 1 digit and store in A
    mov R2,#00h         ;clear R2
    mov R2,A            ;move second 10x+1x digit
    mov B,#00h          ;clears B
    clr A               ;clears A

    pop ACC             ;pops second 100x value into ACC
    mov B,#64h          ;moves value 100 into B
    mul AB              ;multiplies second 100x value by 100 and stores it in ACC
    add A,R2            ;add 100x value to 10x+1x
    mov R2,#00h         ;clears R2
    mov B,#00h          ;clears B
    mov R2,A            ;STORE SECOND NUMBER IN R2
    clr A               ;clear A

    ;first number entered
    pop ACC             ;store first 1x value in ACC
    mov R3, #00h        ;clears R3
    mov R3,A            ;store first 1x value in R3 by moving it from ACC

    pop ACC             ;store first 10x value in ACC
    mov B,#0Ah          ;moves value of 10 into B
    mul AB              ;multiply second 10x digit by 10 and stores in A
    add A,R3            ;add second 10 digit to second 1 digit and store in A
    mov R3,#00h         ;clears R3
    mov R3,A            ;moves added value to R3
    mov B,#00h          ;clear B
    clr A               ;clear A

    pop ACC             ;pop first 100x value into ACC
    mov B,#64h          ;move value 100 into B
    mul AB              ;multiply first 100x value by 100 and store in A
    add A,R3            ;add first 100x value to first 10x+1x and store sum in A
    mov R3,#00h         ;clear R3
    mov R3,A            ;STORE FIRST NUMBER IN R3
    mov B,#00h          ;clear B
    clr A               ;clear A

    push DPL            ;pushes createnums addresses back into stack
    push DPH
    ret

addorsub:
;adds two numbers if user inputs +, subtracts if input is -
    lcall getnum                    ;gets +(A) or -(B) from keypad
    lcall getkey                    ;gets the correct ASCII value key pressed
    lcall sndnum                    ;sends + or - to screen

    mov R6,#00h
    mov R6,sbuf

    lcall crlf

    cjne R6,#2Bh, getsub                    ;if P1.1 bit is set, run getsum
    lcall getsum                    ;if P1.2 bit is set, run getsub
    ret


getsum:
;gets the sum of the two numbers entered and stores the answer in A
    clr A                   ;clear ACC
    mov B,#00h              ;clear B
    mov A,R2                ;move second number into A
    mov B,R3                ;move first number into B
    add A,B                 ;add first and second number and store result in ACC
    ret

getsub:
;subtracts the first number from the second number and stores the answer in A
    clr A                   ;clear ACC
    mov B,#00h              ;clear B
    mov A,R3                ;move first number into ACC
    mov B,R2                ;move second number into B
    subb A,B                ;subtract second number from first number
    ret


displaysum:
    mov B,#64h                  ;move #100 into B
    div AB                      ;divide answer by 100 and store 100x value into A
    mov R2,A                    ;move 100x value in R2
    clr A                       ;clear A
    mov A,B                     ;move remainder of past division, 10x+1x value into A
    mov B,#0Ah                  ;move #10 into B
    div AB                      ;divide 10x+1x value by #10 to store 10x value into A
    mov R3,A                    ;store 10x value into R3
    clr A                       ;clear A
    mov A,B                     ;move 1x value into A
    mov R4,A                    ;store 1x value in R4

    mov R1,#30h                 ;move #48 into R1 because
    mov A,R2                    ;move 100x value into A
    add A,R1                    ;add 100x to 48 to get ASCII code for that value and store sum in ACC
    clr scon.1                  ;clear the ti complete flag.
    mov sbuf,a                  ;move ASCII code for 100x value to sbuf
    txloop6:
        jnb scon.1, txloop6     ;wait till digit is sent

    mov R1,#30h                 ;move #48 into R1
    mov A,R3                    ;move 10x value into ACC
    add A,R1                    ;add 48 to 10x value to get ASCII code for 10x value and store sum in ACC
    clr scon.1                  ;clear the ti complete flag.
    mov sbuf,a                  ;move 10x ASCII code into sbuf
    txloop7:
        jnb scon.1, txloop7     ;wait till digit is sent

    mov R1,#30h                 ;move #48 into R1
    mov A,R4                    ;move 1x value into A
    add A,R1                    ;add 48 to 1x value to get ASCII code for 1x value and store sum in ACC
    clr scon.1                  ;clear the ti complete flag.
    mov sbuf,a                  ;move 1x value into sbuf
    txloop8:
        jnb scon.1, txloop8     ;wait till chr is sent

    lcall crlf
    ret