Analog modem emulator?

[Tony Duell]

> > What did the COmmunications Card consist of? Checking one of my boxes of
> > Apple ][ bits revealed a Super Serial Card (6551-based) and a Serial Card
> > (a bit-banger, a few TTL chips and a couple of PROMs, P7 and P8). It's
> > hard to see how you could have less than that.
> 
> I don't have the card to hand but I have the manual here.  It's real
> simple, like the Disk ][ controller.  Two 74161, a 7474, a 6309, a
> 6850, and a DP8304.

That suprises me. The 6850, of course, is a UART-like chip (well, 
Motorola call it an ACIA, but it handles the serial-parallel 
conversions). 

The Apple Serial Card I have doesn't have any UART, or shift registers, 
or anything like that. Just a few TTL chips to make a 1 bit I/O port, 
line drivers (and an opto-isolator for the current loop function), and 
thr 2 PROMs containing the cotnrol firmware. The serial-parallel 
conversion is done in software on the Apple's 6502. 

So what is suprising that the Apple 'went backwards' from a card with 
hardware serial conversion to a bit-banger. 

-tony