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Commodore A2232 Serial Expansion Board
Launched in 1990, the A2232 is a standard 100-pin Zorro II expansion card for the big-box Amigas (A2000, A3000, A4000). It provides the host machine with 7 additional RS232 serial ports, capable of speeds between 50-19200 bps.
For more serial channels additional A2232 boards can be plugged into the system at the same time. Up to five boards (probably a limitation of the number of Zorro slots in any available machine at the time) giving a total of 36 serial ports are supported.
A2232 Schematics (PDF) (part of 'System schematics - A2060/A2065/A2232' by Commodore International Spare Parts GmbH Braunschweig, West Germany - August 1990, PN-314042-01).
The A2232 has its own MOS 65CE20 processor running at 3.58Mhz and has 16kB of RAM (addressable by the Amiga's 680×0 CPU) leaving the Amiga free for other tasks.
There are at least two revisions of the board:
- Rev 4 boards: 7x MOS Technology 6551 ACIA (Asynchronous Communications Interface Adapter) chips
- Rev 6 boards: 7x CSG (Commodore Semiconductor Group) 8551 ACIAs (1984 released HMOS-II variant of the 6551)
Silkscreen next to the Zorro connector says BERLIN/FISHER indicating the design was made by Creg Berlin and Terry Fisher.
The board came with user manual (missing, anyone have a scan?) and seven 80 cm long adapter cables that provided the (then) standard DB25 connections.
Enhancements and modifications
Up to 57600 on all ports using a custom device-file and hardware modification: a2232tuning.lha on Aminet by Markus Marquardt.
Several sites also refer to mods for up to 115200 bps speeds (on all ports? Link?).
Amiga.resource.cx also has a photo of a board with a title "Rev 6 board with RTS/CTS handshake mod".
Another modification is to replace the 1.84Mhz oscillator with a 3.68Mhz one. This doubles the baud rates but the software won't know about this so the user must keep this in mind when using the board.
Serial port pinouts and cables
The connector nearest to the Zorro connector of the board (leftmost) is the first serial port.
The board uses seven mini 8-pin DIN connectors (similar to the serial ports in Apple Macintosh computers) to fit all the connectors to the end plate of a single expansion board.
The pins 1 and 2 can be reversed on any port using jumpers located on the jumperblock next to the connectors:
If you need to build your own cables and you are using solderable mini din connectors, make sure it will fit deep enough into the socket when the board is inside the computer's case. A good source for molded connectors and cables are 8-pin Apple serial cables that have the same connector on both ends of the cable (and are fully connected). Cut one of those cables in half and you'll have a better-looking and mechanically more reliable connectors (not to mention that soldering those mini-din connectors is a real pain!). DB25 and DB9 connectors are still widely available.
If you only plan to build a single cable and use that with a modern machine thrue an USB-serial adapter (9-pin), you can build a null-modem included connection that plugs straight into the USB-adapter.
Thanks to mackbw on English Amiga Board forums for providing the pinouts of the original cables!
Using the serial ports
In Amiga UNIX the first port of the A2232 is available at /dev/term/ql00, second one ql01 and so on, thrue to ql06.
Probably the main selling point of the A2232 was the ability to connect several serial terminals to an AMIX machine running as a server.
Use the pmadm command to start a login shell at any of the serial ports:
pmadm -e -p serial -s ql00
This enables a shell in the first port at the default speed of 9600 bps (the defaults are defined as the 'serial' preset in /etc/screendefs -file).
A real vintage dumb terminal (or a device like PockeTerm from Briel Computers (sadly no longer available)) or a modern PC with a serial port and a terminal emulator can be connected to the port and used to log into the machine.
In Workbench the ports can be accessed using the serial.device driver (ver 33.11 from 1990 and newer, install disk available at Amiga.resource.cx) with the following unit numbers:
Unit 0, the default setting can be set in Workbench's Prefs / Serial-panel. It can be set to any of the available serial units in the machine.
If several A2232 boards are installed (up to five), the second board's unit numbers are 9-15 and so on.