AH2500A to IBM PC Type Serial Port
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To attach an Andeen-Hagerling 2500A bridge to an IBM PC Type Serial
Port and command the bridge from the PC:
The official documentation is in the "Operation and Maintenance Manual."
Here are some shortcuts. You need a cable to physically connect,
an unused serial port on the PC and a terminal emulation program running
on the PC.
The connectors are of type DB-25 (25 pins) on the bridge and some ports
of the PC. Other serial ports on PCs have DB-9 (9 pins). Bridge
and PC serial ports are all male. PC parallel ports are all female.
Do not cross connect serial and parallel ports: the result is usually permanent
destruction of the parallel port.
If you have a DB-25 male on the PC, the connection is usually simple.
A cable is needed with female DB-25 on both ends, and only pins 2, 3 and
7 are required. But pins 2 and 3 must cross (that is, 2 on one connector
attached to 3 on the other connector of the cable and vice versa).
This is usually called a null modem cable.
If a "straight" (not null modem) cable is available, with pins 2, 3 and
7 run through the cable without 2 and 3 reversing, enter the command
"BAUD .1" on the bridge front panel and also "STORE BAUD 1" if you like,
so the change is permanent. Henceforth, the bridge will do the needed
reversing internally. Contrapositively, enter "BAUD .0" and "STORE
BAUD 1" to undo this.
If you have a DB-9 (male of course) on the PC, you need pin 5 on the DB-9
connected to pin 7 on the DB-25 (for ground), and pins 2 and 3 on the DB-9
connected to pins 2 and 3 of the DB-25 without reversing.
Usually, there are several serial ports on a PC, and you need to know which
you are using. If you can't tell, try finding out which ports are
already attached to other things, so narrowing down the number of possibilities.
In any case, you can always try them all. Usually, the PC serial
ports are named COM1:, COM2:, COM3: and COM4:.
Attach the cable. If your computer goes berserk, you've connected
to a port with some driver running on it, and so disconnect the cable,
reboot and see what you have done wrong.
Running the Terminal Emulation
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The standard terminal emulation program is called "HyperTerminal" and is
on Windows 95 and Windows 98, though probably in different places in the
Start Menu. A reference to the program is probably under Programs|Accessories
in Windows 95, and in Programs|Accessories|Communications in Windows 98.
This selection may ask you immediately if you want a new connection (that
is, the program is running) or merely drop you in a folder. In this
latter case, find "Hypertrm.exe" (or maybe just "Hypertrm") and select
to run it.
Now you are asked to name the connection, which is anything you please
and can easily remember, or perhaps you must select from the menu File|New
You will then configure the connection through a dialog box, an entry of
which will identify the device, usually, patronizingly, your modem.
You aren't interested in a modem, but the list should include entries of
the form "Direct to COM<number>:" and select that, where <number>
is the port on the PC to which the cable is attached.
Press the button labelled "Configure" in this first dialog box to make
another dialog box pop up that has the RS-232 configuration: including
baud rate, data bits, parity, stop bits and flow control.
Select these configuration parameters to match the bridge defaults (you
can tweak them later): 9600 baud, 8 data bits, no parity, 1 stop bit and
Xon/Xoff flow control.
Press OK until the dialog boxes clear and you return to the main window
Press Enter several times as an experiment. You should see a prompt
from the bridge ">" (a greater than sign). Then type "single" and
press Enter to see that the bridge takes and reports a measurement to confirm
that it is working.
In case of trouble: try selecting from the HyperTerminal menu: Call|Disconnect
and then press Enter again as an experiment. (Sometimes configuration
option changes don't get a clean restart without this command). Also
try toggling power on the bridge for the same reason. If you are
relying on a "BAUD .1" command (see above) and did not do "STORE BAUD 1"
then "BAUD .1" must be entered again on the bridge front panel after power
is reapplied. Also try quitting HyperTerminal entirely and restarting
If the configuration seems bad, you can get back to the appropriate window
in HyperTerminal by selecting from its menu File|Properties.
If all goes well with HyperTerminal, select from the menu "File|Save" and
the connection configuration will be available next time by the name you
entered for the connection this time.
There are many interesting problems that could occur that aren't described
here. Most of the problems are common to all RS-232 connections with
PCs, so any generic documentation on the topic is useful. And, although
it takes a while to learn to use it, an RS-232 diagnostic tool with LEDs
and jumper wires is very handy. A useful hardware remedy is always
to have a selection of RS-232 cables, adapters and doodads (variously called
gender menders, sex changers and null modems) and attach these at random
until something good happens.
Eventually, while connected via RS-232 to the bridge, you will want to
enter the command "define terminal video".