hi,
you should read datasheet more careful especially chapter "More about Mode 0". It is not possible to connect two MCU via UART at mode 0. At mode 0 there is no UART but shift-register instead. As result:
1) If MCU sends byte (after you load something into SBUF) then pin RXD transmits data bits and pin TXD transmits shift clock.
2) If MCU receives data (it starts after you do condition: REN=1, RI=0) then pin RXD receives data bits and pin TXD transmits shift clock.
So:
a) you may connect pin RXD1 to RXD2. But what is about TXD1 and TXD2? They both transmit shift clock due action in progress.
b) there is no "start to receive condition" in your scheme. You must understand: in Mode 0 reception starts not with start bit but with condition REN=1, RI=0 instead.

Regards,
Oleg