Hi,
From what I can tell, you can't preload POSCNTH or POSCNTL
Sure you can, I find no problems doing that.

Another item that puzzled me is that the datasheet mentions that MAXCNT value is 1527h
Not sure where you got that number from but MAXCNT is setable to anything between 0 and 65535.

I'm trying to do as simple encoder for menu sleection and would like to set POSCNT in the middle so that I don't have to mess with rollover in either direction
MAXCNTH = 128 works just fine here.

Code:
Test:
  HSEROUT["Program start",13]
  HSEROUT[DEC PosCntH*256+PosCntL,13]
  Pause 10
  PosCntH = 128
  HSEROUT[DEC PosCntH*256+PosCntL,13]
  PosCntL = 1
  Pause 100
  HSEROUT[DEC PosCntH*256+PosCntL,13]
Program start
0
32768
32769
/Henrik.