What's the right way to add even or odd numbers in this assembly code

Question

For example I have a file (codes.txt) with these code nums

CODE1   fcc "3392236"
CODE2   fcc "1234550"
CODE3   fcc "7654361"
CODE4   fcc "1212223"
CODE5   fcc "1233211"
CODE6   fcc "1232343"

Next, a subroutine called readCode_Driver which job is to help reading these numbers with another subroutine called toInteger.asm. The readCode_Driver.asm file goes as follow:

NUMBEROFCODES   equ     6       ; Six CODEs to process
LENGTHOFCODE    equ     7       ; Each code is 7 digits
PROGRAMSTART    equ     $2000   ; Executable code as in (programming code) starts here
STORAGE1        equ     $1000   ; Storage starts here for original code numbers

org     STORAGE1
CODES
#include codes.txt

    org     ProgramStart
    lds     #ProgramStart

                            ; Setup to use toInterger
    ldx     #CODES           ; point to first digit of NUM1 ex: 3
    ldab    #LENGTHOFCODE    ; code's length
    clra                    ; loop counter



ConvertCODEs

    psha                    
    pshb                    

    jsr     toInteger         ; Convert from ASCII to Integer


    pulb                    ; Retrieve CODE's Length (called a POP)
    pula                    ; Retrieve Loop Counter

    inca                    ; Setup to loop again
    cmpa    #NUMBEROFCODES   ; All six codes converted?
    bne     ConvertCODEs     ; No, so continue on looping
    swi                     ; All six CODEs converted?

#include toInteger.asm            ; subroutine to test with this driver
    end

This is my toInteger.asm file and its content:

toInteger ldaa    0,x                             ; get ASCII value
    suba    #$30                            ; convert to an integer
    staa    0,x                             ; store integer
    inx                                     ; point to next value
    decb                                    ; one less value to do
    cmpb    #0                              ; Is this the last ASCII value?
    bne     toInteger                         ; No, more to do
    rts                                     ; Yes, so we're done

to validate these code, I need another subroutine called addeven.asm. This subroutine is suppose to add even numbers in the codes. For example, CODE1 has 3392236. The even numbers are chosen from this position 0 1 2 3 4 5 6. In CODE1, even numbers would be 3(pos 0),9(pos 2),2(pos 4), and 6(pos 6). Odds numbers would be 3(post1),2(pos3),3(pos5)

Question is, how do i take the even numbers in code1, multiply each individual even numbers by 2, and then add them in assembly language. It goes like this 2*3,2*9,2*2,2*6 then add them like this 6+1+8+4+1+2. For these code 18 is 1 and 8 so I added them like 1+8. The micro controller is the dragon 12 68hc12

Answer 1

Somehow 68xx series comes to mind...

The multiplication by 2 can be done easily by shifting, and skipping every second byte can be done the same way you did the conversion, except INCing the x twice. With odd bytes, you INC x before the call.