A question!!! (OpenSourceGPS,ogs,frame_ready)

Hi everybody
I got a problem in ogs,( and the base of it osgps)

In function main of OpenSourceGPS  it checks channels frame_ready to see
if it is one or not,
In function pream of  OpenSourceGPS it checks channels t_count to see if
it is 1500 or not,
In function ch_track of  OpenSourceGPS we call pream:
void ch_track(char ch)
{
         .
         .
         .
	 pream(ch,chan[ch].bit);   // see if we can find the preamble
	 chan[ch].message[chan[ch].t_count]=chan[ch].bit;
	 chan[ch].t_count++;
         .
         if (chan[ch].t_count==1500)
        {
      	     chan[ch].n_frame++;
	    chan[ch].t_count=0;
       }
        .
        .
}

Looking to the above code carefully It seems that it never calls pream
function with t_count==1500, but as I mentioned, in pream we check if
t_count equals 1500 to set the frame_ready variable(wich it never happens!!!).

The question is when the frame_ready will be set?
or better to say when the navmess function will be called?
(The exact problem  is in ogs).

best regards
Behzad Chenaghlou