Hello!
Previous T89C51RD2 has been made by Temic. Now Temic Electronics is part of Atmel. So, you have to look for the datasheets at ATMEL-WM web site (WM means Wireless Microcontrollers). I have sent some addresses and informations to you.
Erik - do you read this? A few days ago you've asked about remote programming. Maybe T89C51RD2 is good solution for you. Its programming is very intersting. You have only to build RS232 driver (using MAX232, 202 or similar to these), join the serial cable to your PC and you can write/read the program. T89C51RD2 can be enter into programmng mode by external (driving PSEN line) or internal (using bootloader program). Look at www.atmel-wm.com/products/ for details - maybe it is solution of your problem.

Regards,
Jacek