in the ISR by the line

	djnz	R3,	EXIT

DJNZ will affect carry. So formally, he does need to save PSW.

BUT: because his main loop is so shockingly simple, he will never notice the ISR thrashing PSW, so in practice, in this particular case, he will not benefit from saving either the accu or PSW.

To Jeroen:

I would also like to point out that the SEND subroutine is bad (do not reset TI manually before sending a character! What if the UART is still busy?) and that it's called from within the timer ISR. Since the SEND routine polls TI in a tight loop and doesn't return until TI goes high again, the timer ISR will not return until the UART has sent the character out completely, this makes the timer ISR waste a lot of cycles. I wonder why you made it a subroutine anyway, since you only use it once. Why not simply include the write to SBUF in the timer ISR directly?
Now I know it will probably work for a simple project like this, but it's not good practice. If you ever want to make more serious programs, "techniques" like "doing potentially time consuming things inside an ISR" and "JNB SOMETHING,$" will kill you. Unlearn them quickly!