.Data
  frequency DW 0, 260, 300, 330, 350, 390, 440, 500, 520, 590, 660, 700

mov EAX, frequency
  mov ECX, 0  // as a counter

mov  ecx, 0                  ; initialize counter
    mov  edx, OFFSET frequency   ; get address of the first element
DoLoop:
    mov  eax, DWORD PTR [edx]    ; get value of the element
    ...                          ; do something with that value, now in the EAX register
    inc  ecx                     ; increment counter by one
    add  edx, 2                  ; increment pointer by size of an element
    cmp  ecx, 12                 ; compare counter against 12 (total number of elements)
    jl   DoLoop                  ; keep looping while less than 12

cmp  X, 700       ; where X is some register or memory location that you want to test
jne  BranchLabel  ; where 'BranchLabel' is the label to jump to if X != 700