each 4.6ms (each TDMA frame)
only exception on TS0, which can have a different frequency list than the other timeslots. Therefore you will see this :
TS1…TS7 : same freq
TS7 (TDMA n-1) to TS0 (TDMA n) : chg freq
TS0 (TDMA n) to TS1 (TDMA n) : chg freq
TS1…TS7 : same freq
and so on…