RS-232 Interface Board  (250-1031)     Features       Faxback Doc. # 5568

The Tandy RS-232 PLUS Interface Upgrade Board is an RS-232 standard
input/output (I/O) interface that enables you to connect serial data I/O
devices (modem, printer, plotter, etc.) to your Tandy 1000 or 3000 series
computer. The board greatly expands the communication capabilities of your
computer when you use it with an external modem and the appropriate software
so that you can:

* Access major information services (subscription to a service is required)
* "Talk" with other computers as either host or a terminal computer
* Use serial printers and plotters

After you install the RS-232 Board and connect another computer (or some other
external device), remember that communication is not automatic. It requires an
application program written especially to operate, or drive, that device.

Commercially available programs include the driver so that all you have to do
is load and run the program. For example, you can begin RS-232 communication
by taking advantage of Telecom, a telecommunications feature included with
DeskMate. Telecom lets you access Dow Jones News/Retrieval, CompuServe, and
other information services.

But what does the RS-232 board itself really do that enables communication?
Simple. At the communication source, it takes parallel data (characters
transmitted one at a time along one path). At the receiving end, it converts
the data back.

The advantages of serial transmission are that it requires only one
transmission path and that it eliminates problems of data synchronization
associated with parallel transmission.

FOR THE ADVANCED USER

The RS-232 board incorporates an Asynchronous Communications Element (ACE)
that performs the serial-to-parallel data conversions. The features of this
ACE are discussed in the chapter "Programming Information."

To use a non-standard RS-232 device, you need to write a special device driver
for it. The chapter on programming the ACE provides the information you need.

The ACE has a baud rate generator that you can program to operation from 50-
to 9600 baud. You can also program the ACE to add or remove start bits, stop
bits, and parity bits. It supports 5-, 6-, 7-, or 8-bit characters with 1, 1
1/2, or 2 stop bits.

(smm 08/03/93)