assembly - adding 16 bits registers -

i have code

addint:         add cx, bx         cmp cx, 0ffffh         jbe convert 

i'm trying add cx , bx registers, each have same value of ffff, instead of getting 1fffe, fffe, , when try use jbe jump convert loop, jbe istruction nothing because ecx register contain fffe, not 1fff, how can fix code make ecx contain 1fffe , how compare check if still 16 bits or not. cannot use 32 bits registers make thing more complicated

thank in advance

addint:      clc            ;clear carry flag      add cx,bx      jnc convert    ;jump no carry      cmp cx,fffeh   ;this needs true, ffff+ffff succeed                      because generates carry , matches cmp      jnz convert    ;will let through 

this work, it's limited , simplistic

to "count" carry use adc dx,0 inserted after jnc convert

the carry flag set if register goes round clock, acts single bit

add ffff+2 set off, giving +ve carry flag , 0001 in register

you can store flag count in separate register adc [other register],0

using carry flag allows slap registers count

1,208,741,363,432,547,555,475,424 4x16 bit registers

which quite lot , miles better 65,534