Analog modem emulator?

6 Aug 2005

...
   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

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

2000

1999

1998

1997

Analog modem emulator?