RAW for Canon Powershot A540?

I have successfully installed CHDK on a SD card inserted in my Powershot A540. I would like to know how do I shoot RAW pictures? What are the setting in the <Alt> menu of the camera that should be done? What are the in-camera settings to shoot RAW photos using Canon Powershot A540 digital compact camera? What are the RAW parameters that should be set in the CHDK in-camera menu? If someone can advise, it would be wonderful. Thank you.

I shot some pics with the file name as: CRW_xxxx.CRW & IMG_xxxx.CRW. But these files do not open up in Adobe Photoshop Creative Suite 5 (CS5) extended edition. Which image editing / RAW processing software should be used? Any links?

ANSWER: I got it!

Download "DNG for Powershot-2" from link given below:

Convert the files shot by the camera into '.dng' format using this DNG for PS2 software. The converted files when opened in 'Adobe Photoshop CS5 extended edtion' are RAW files.

Thanks to CHDK. Superb. Keep up.