Siemens S7-1200 Firmware Update help

Hi folks,
Just doing a project where we are having to get bits of data from various plcs (get & Puts etc) and adding a CP module into the mix.
Only one of the older CPUs requires the firmware updating its 1200 running V2.2

Can I just upgrade the firmware to the latest version 4.3? or do I have to gradually have to go thru all the stages of updates 2.2 to 2? to 3.? to 4 etc

TIA

The 1200's with older firmware cannot be upgraded to v4.0
That goes for v2.x and v3.x
If you have a v4.0 it can be upgraded to the latest v4.x firmware.

The only upgrade path is to replace the PLC and put the old one on ebay (there are other sites giving online auctions). I have been keeping the old ones and programming them as machine simulators.