INS8073 interface?

Hi all, I recently found several INS8073 (aka SC/MP III, with Tiny Basic in ROM) which I want to build a complete system for. I have the datasheet for the 8070 which is the ROMless version. This gives of course hints how to add RAM. The question is how to talk to the BASIC interpreter. From the 8060 (the SC/MP II) with NIBL BASIC I know that the CPU itself uses two pins to implement a 1200Bd serial line which just needs some additional RS232 drivers to work; serial I/O is done by software in the NIBL ROM. I assume this works the same for the 8073. Unfortunately, the SC/MP III does not have these specific pins. So: how does the interface look like for the 8073? Does anyone have a specific application note for this processor? Regards & THX in advance Holger