What is the maximum baud rate possible with 89c51rd2, is it possible to achieve speed of 115 k baud or greater??
http://www.keil.com/c51/baudrate.asp
The problem with achieving a high baudrate is typically in the ISR, not in the UART. This, of course, require that you uyse a "UART crystal" such as 11.0592 and not a "processor crystal" such as 12MHz. Erik