Vector ZCB User Manual page 36

vector ZCB Single Board canputer
2.4.5 How to connect many low speed asynchronous acoustic couplers and moderns
This section is applicable to many acoustic couplers and moderns which
carry out asynchronous camnunications at rates of 1200 baud or less. It is
almost always applicable for asynchronous couplers and moderns operating at
300 baud or less. Specifically, it is applicable to moderns and couplers
which require only three RS-232C lines corning from the canputer: Transmit
Data (line 2) , Receive Data (line 3), and Signal Ground (line
7).
Because the ZCB board is wired for direct connection to a terminal, you
cannot simply connect the ZCB serial I/O cable to the modern. This is
because both the modern
and
the ZCB serial p::>rt in its normal configuration
are Data Communications Equipment (DCE), and therefore both expect to
receive data on line 2
and
to transmit data on line 3. Another problem is
that most moderns and couplers have female sockets, and the D8-25 connector
at the end of the ZCB serial I/O cable is also a female socket.
One solution: create a three line cable with male DB-25 connectors at
both ends. Wire line
7
straight across,
and
cross lines 2 and 3. In other
'W:lrds, connect pin 2 of one connector to pin 3 of the other, and vica versa.
Such a cable will work with any modern or coupler requiring only three lines.
Connect one end of the cable to the D8-25 of the ZCB Serial I/O cable and
the other end to the
modern
or coupler.
We strongly suggest that you do not roc:xhfy the ZCB board itself or the
ZCB serial I/O cable, in order to cross lines 2 and 3. By modifying or
adapting the external cabling instead, the computer itself remains standard,
and the serial p::>rts can easily be used for connecting to a terminal or
other kind of peripheral
if
ever required.
2.4.6 Oonnecting additional RS-232C handshaking lines
If you are using a tenninal which requires handshaking over and above the
+12
VDC
supplied on lines 5 and 6, or
if
you are using a modern or coupler
which requires any handshaking at all, that is, requires more than a three
line connection (lines 2, 3 and
7),
then continue reading this section.
The following table lists all 25 RS-232C lines by name, number, and
source,
and
indicates what subset of these are connected to the ZCB board
via the ZCB Serial I/O cable. For this subset, the table specifies each
line's pin number on the 16-pin socket connected to the end of the ZCB
Serial
I/O
cable. The table also lists those lines which are connected to
carnp::>nents or jumper pads, in the factory configuration of the board, and
what they are connected to. IU16-13" means it is connected to pin "13" of
u16.
II
GND
II
indicates the line is connnected to Ground in the factory
configuration.
Rev. I-B 6/11/80
2-15