89c52 uart baud rate
Xtal is the minimum requirement for 115.2kHz baud rate.
Let's imagine,
In standard 51 architecture, we need 12 clocks for executing an instruction.
At 22MHz Xtal, instructions are executed at 1.8 MHz.
Roughly, 12.8K bytes are transmitted in a second.
So, your processor must finish all the receive and transmitt job in 141 instructions (1.8MHz / 12.8K).
It would be a tough job.
Added after 5 minutes:
Xtal is the minimum requirement for 115.2kHz baud rate.
Let's imagine,
In standard 51 architecture, we need 12 clocks for executing an instruction.
At 22MHz Xtal, instructions are executed at 1.8 MHz.
Roughly, 12.8K bytes are transmitted in a second.
So, your processor must finish all the receive and transmitt job in 141 instructions (1.8MHz / 12.8K).
It would be a tough job.