Please get the current 5.2 version for S12, you can download the evaluation version on the following link
CodeWarrior Dev Tools for HCS12(X) MCUs|NXP
Once you download this version, you can go to previous tab to get the previous v5.1
You have some other IDE options on using this device too .
S12D MCUs|16-Bit Microcontroller|NXP
Hope this helps
Please get the current 5.2 version for S12, you can download the evaluation version on the following link
CodeWarrior Dev Tools for HCS12(X) MCUs|NXP
Once you download this version, you can go to previous tab to get the previous v5.1
You have some other IDE options on using this device too .
S12D MCUs|16-Bit Microcontroller|NXP
Hope this helps