[SOLVED] sending signal to top command

earlier this year i read something somewhere (i forgot where, it could have been here) that suggested a certain signal sent to the top command would cause it to refresh its display. at that time i thought of a use for that but did not have time to implement it. i did try it manually and it worked. today, i had a little time, but i could not find any man page or google result that tells me what signal that is. i forgot which specific signal it is. i tried SIGUSR1 and SIGUSR2 but they just cause top to exit.

does anyone know of this signal?