To be sure what kind of memory lay-out is used, i usually try to firstly see if i can get hold of a already readed-out file the specific ecu.
if it's a 1meg file, you have a 800-layout
if it's a 512kb file, you have a 400-layout.
Another way to approach : choose for 800-layout, and try to readout. If succeed, and it is a 400, some hex-editing can be applied to
cut-off the excessive 512kb. Or do a re-read in 400-layout mode, afterwards.
Go try it out
Cheers,
PvL