I would like to know if there is any tool for migrating from ARM mcu's to Atmel? can any one help me on this topic?
Although I was a user of Protel (then), I don't have Altium so I can't give you much help on this.
Whether you are doing schematic capture or PCB layout, generally a part can be found through its category (e.g., ADC, DAC, EEPROM, LDO, microprocessor) or through its manufacturer (e.g., Analog Devices, Atmel, NXP, ST, Texas Instruments). If you can't find it in the pre-installed libraries, my advice would be similar to Jens' reply. When you have to create your own part, consult the datasheet to get the package type. You can use the generic footprint as is but if the manufacturer has a suggested dimensions for the pads you can have them modified.
Thanks for your recommendation and I guidance. I think this is the right
one.
Regards
Norman