Thanks Henrik. This explains a lot. I do not have an any device currently with me so I could not measure it at the moment.
Few things come to mind - What is the actual acceptable delay/error @ 2400 baud? Is it upto 20uS - 40uS that the transmission will not be affected? This would help, as I may use an higher oscillator, lets say 20MHz and bring down the latency if possible. Secondly, DT_INT also has assembly routine type interrupts, could you please check those for me, what is the latency there. If the way exists and all fits in, I would like to make this work using DT INT only without adding another PIC to handle the RF part.