Hi,
If you would like to use processor expert for S12XHY family, you should install Codewarrior v5.1 and the patch of CW12_V5_1_PE_V3_05_SP.exe, NOT use Codewarrior v5.2 which does not support it.
CW12_V5_1_PE_V3_05_SP.exe could be gotten through the link.
S12GA48 Device Initialization
Codewarrior 5.1 could be gotten through the link.
http://www.nxp.com/lgfiles/devsuites/HC12/CW_HC12_v5.1_SPECIAL.exe
