Apple ][ boards (mostly

Tony Duell ard at
Fri Aug 12 19:07:03 CDT 2005

> Apple's official RS232 interface for the ][ used only level shifters from

There are at least 3 'official' RS232 interfaces for the Apple ][ -- the 
bit-banger card, the comms card (6850 based) and the super serial card 
(6551 based). 

> TTL to +- 12.  The 6502 would fiddle the levels and watch the control
> lines in software.

That sounds like the bit-banger card. I have a couple, I have the manual 
somewhere. I've also heard that one early Apple manual (which I don't 
have) contains code to bit-bang 110 baud serial data through one of the 
outputs on the games connector, and that that was the original way to get 
printouts from an Apple (convert to current loop, add an ASR33). 

> If you have a controller with a UART on it, then it will need a driver
> chip and may not be useful with some apple aps.

Most of the serial cards, including the bit-banger and the other 2 Apple 
ones have firmware PROMs on them, which cotnain the drivers with the 
standed PR#n, IN#n interface. 

> The card I have has a 12 or so pin ribbon cable actually fixed to
> the board by a header, and it dangles thru the apple2 slot and is
> clamped in place there by a metal bracket that pinches the cable
> and the case to make a firm installation.

Both the bit-banger and the 6850 card have that sort of construction. 

> As I said, it has no chips larger than the 14 or 16 pin packages IIRC.

I thought the firmware ROMs (there are 2 on the bitbanger, P7 and P8) 
were 20 pin chips.

> I ran some sort of terminal emulator on it at one time, and I remember
> it had trouble over 1200 baud or so.

You were lucky. I had problems with it at 300 baud...


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