Gas skid, flow computer with a Modbus TCP port, S7-1200 CPU 1214C with MB_CLIENT, TIA V16. Reading the twelve analog inputs at 30001 to 30012 works, all twelve values arrive and match the transmitters, I proved the loops first.
The totals and the corrected flow the manual lists at 7001 to 7016 won't come. MB_CLIENT with MB_DATA_ADDR 47001 gives STATUS 16#8383 and the flow computer's own comm log says exception 02 illegal data address.
I tried 47000 and 47002 in case it's an off by one, and read lengths of 2, 4 and 16, same thing every time. Is the register area above 7000 locked on the device somehow? The vendor's slow to answer and I'm stuck on it. Should I maybe be reading those register tables in the manual differently, given the 30001 block comes in fine and the 7000 one won't?
Off by one is my first guess always, 47001 in the block being register 7000 on the wire. You've tried both sides, fine. Post the manual page for those totals, the table heading matters more than the numbers.
The page heading says "Input Registers (3xxxx) read only" and then 7001, 7003, 7005 as float pairs. Photo of the page attached. The setpoints are in a separate table headed "Holding Registers (4xxxx)".