Clause 8.7 of E1-11 (DMX512-A) says ....

"There shall be no minimum number of data slots on the data link. DMX512 data packets with fewer than 512 slots may be transmitted, subject to the minimum timing requirements of this standard – see clause 8.10 ..."

Clause 8.10 refers to table 6 of timings FOR TRANSMITTERS which says Minimum DMX512 packet length transmitted shall be 1204 microS of which minimum BREAK shall be 92 microS and minimum MAB shall be 12 microS.

This leaves 1100 microS for N+1 channels (one extra for the Start Code)

1100/44 = 25 thus 24 minimum channels are required if you want to satisfy DMX512-A clause
8.10.

But this does not mean that U cannot transmit lesser channels physically. The problem may arise if a reciever is actually coded to check for those 24 channels.

Ujjal