I'm not admitting to being too old for the list ;) but I remember working with 
approx 5" by 8" cards in the '60s where each card was what became the simpler 
7400 series ICs, like a quad 2 input NAND or such. Each card had a few metal 
can transistors, some resistors and a few caps. Hand soldered too IIRC.

If my MEMORY isn't inverted, I remember that it took less components to make an 
inverter than a buffer, which makes sense to me as I write. I could probably 
confirm that by digging out an old TI TTL databook, but maybe another day.

So, my guess would be cost and space made it easier to make inverting ones in 
the discrete days, and the designer could just arrange his logic to suit. 
Eventually these card designs 'gelled' into ICs and standard ways of using them 
(cookbook designs).

-Skip


Wouter van Ooijen wrote:
> 
> I agree. But my question was why the TTL 'version' of RS232 (the 
> interface between a UART and the driver) is inverted wrt. the RS232, 
> which requires the driver (besides shifting the level) to invert. Was 
> the inverting driver first and did the UARTs follow, or was it the other 
> way round?
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