in section 3.2 where it says the minimum on Vdd is -8.3 and the maximum is 9.7. I think they left off the minus sign and reversed the two. It's not the first time this sort of thing has happened.

In any case, I'd not recommend applying any voltage higher than Vdd, and I'd not recommend applying any voltage to Vdd that exceeds Vss by more than -8.3 volts.

Aside from the power requirement, which a MAX232 won't meet, your intitial idea of powering the ROM from the RS232 interface supplies was, IMHO, on the right track. The only issue is where between the ROM's Vdd (+5 volts) and it's Vss (-5 volts) you set your logic GND. With the RS232 drivers/receivers, it's trivialized, as they're happy so long as one extreme is -3 volts below its logic GND and the other is higher than +3 above it.

I've not read enough of the datasheet to tell you whether a 0-volt level is a one or a zero, though, nor do I plan to do so. That part's up to you, Sam.

RE