Thanks to all who responded to my last thread it was a great help. What I figured out from that is I want this setup on my AT89C52 chip -

Timer0 = RTC
Timer1 = Baud rate generator
Timer2 = Event counter

My goal is to be able to set Timer0 through the serial port plus time how long it takes and thats where I'm stuck, once Timer0 is interrupted by RI being set how do I, start Timer2 counting, recieve data from the serial port, stop Timer2, calculate how long it took to recieve the data, return to RTC?

My thoughts so far:

ORG 0023H
PUSH ACC
PUSH PSW
CLR TR0 ;Stop Timer 0
MOV SM1,#10h ;Set serial mode 1
MOV TMOD,#20h ;Timer 1 in Auto-reload mode
MOV TH1,#0FDh ;Reload value for 19200 baud @ 11.059 Mhz
SETB TR1 ;Turn on timer 1
MOV A,PCON ;Get current value of PCON SFR
SETB ACC.7 ;Set the SMOD bit
MOV PCON,A ;Update the value of the PCON SFR
MOV A,SBUF
CJNE A,#'A',EXIT_SI ;If Acc not= A exit and start again
CLR TI ;Clear TI
MOV SBUF,#'Z' ;Move Z into SBUF
JNB TI,$ ;Pause until TI bit is set (sending back
conformation of RCV)
JNB RI,$ ;Pause until RI bit is set (Awaiting
next transmission)
CLR C/T2 ;Make Timer 2 an interval counter
MOV TH2,#HIGH(RESET_VALUE) ;Set the high byte of the
reset value
MOV TL2,#LOW(RESET_VALUE) ;Set the low byte of the
reset value
SETB TR2
;total mental blank here :)