Experimental Physics and
Industrial Control System

Overwriting pfield does cause problems.  When you post the array, you have to post all three pfield addresses, because you can't know which was in use at the time a client connected.  (As you know, clients actually connect to array addresses, not to fields.) There are three pfield addresses, because buffers are not allocated until a detector field is first used, so the first address is the null array, and the other two are the actual data buffers.  The posting only alerts clients that new data is available; the real buffer address isn't specified until the client calls get_array_info().  It's awkward and unsatisfying, but it works.