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Single Board Computer
Always insert the connector so that the riboon cable emerges toward the
top of the board.
You can double check this by checking that the
"1"
on the
connector corresponds with the
"1"
printed on the board next to the socket.
Then install the DB-25 at the other end of the cable into one of the
available sockets at the rear of the computer, or wherever convenient.
The l:x>ard canes wi th one serial I/O cable.
Many RS-232C serial terminals and printers, particularly those working at
1200 baud or less, require none of the RS-232C handshaking lines.
Some
require that one of these handshaking lines be held at +12
VDC.
In either
case, you can plug these peripherals directly into the DB-25 at the end of
the serial I/O cable without modifying the board at all if you are using
stnadard Vector Graphic software, because the software holds the rrost camron
handshaking lines at +12 VDC - lines 5, 6, and 8.
Note that the ZCB does
not require any hardware handshaking signals from the peripheral in order to
~rare.
- -
If you are not sure whether the board will work without rrodification, try
it before attempting to add additional handshaking signals.
Generally, to
make sure that you are connecting all the necessary lines, use a 25-wire
ribbon cable between the DB-25 at the end of the serial I/O cable and the
DB-25 connected to the peripheral.
The ZCB board does not generate
undesired inhibiting signals on any of the lines.
NOI'E:
If you are writing your own software, you will have to program the 8251
on the ZCB to control any handshaking lines required by the peripheral
device.
If
it is simply a matter of holding high or pulling Iowa line, you
can simply strap the appropriate pin with a source of +12V or GND at the
connector before it even comes into the canputer.
Lines controllable by
software are listed in the table: Additional RS-232 handshaking lines
available.
If a 25-wire cable is not possible, then attempt the connection using
three wires, connecting RS-232C lines 2, 3, and 7 from the DB-25 at the end
of the serial I/O cable to the same pins on the DB-25 which plugs into the
peripheral.
(Receive-only printers that do not generate acknowledgement
signals, such as Teletype or D:?cwriters, do not require connecting line 2.
It is never necessary to connect line 1 - protective ground - because the
ZCB does not ground it.)
If
this does not work, then the peripheral may
require one of the RS-232C handshaking lines.
The two most common RS-232C
handshaking lines required by serial peripherals are Clear to Send (line 5)
and Data Set Ready (line
6).
These two lines are held at +12
VDC
by
standard software.
The manual for your peripheral should specify if any are
required.
To connect one or more, simply connect a wire between the
corresponding desired pin numbers on the DB-25!s at both ends of your
external cable, in addition to the three lines (2, 3, and
7)
given above.
Remember that you do not have to worry about this if you simply use a
25-wire ribbon cable.
2-12
Rev. I-B
6/11/80
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