There is no AT90s52. you probably mean the AT89c52 which is the 8052 family (basically the same as the 8051). you can find a lot of info on 8052.com or ATMEL website (datasheets)
Hi .. There are NO AT90S52, I Think you mean AT89S52. This is mcs51 (8051) family. Most structure are the same as 89C52 but it support insystem programming (ISP). The same as AT89S51, AT89S53 and AT89S8252. AT89S52 have 8K Flash...