9
CHAPTER 3: Installation
Lead Pass-Through
This function allows the COS II either to pass
hardware-handshake leads to connected devices or
to block them. If they are blocked, the leads will still
be used to regulate the internal buffer of the
Switch. The following table shows the behavior of
the COS II for different combinations of devices.
Table 2. Leads Passed Through.
Table 3. Settings and Functions for Switch SWF
NOTE
To use the saving function of the
SW540A-R3, DIP switch F position 1
must be OFF.
Switch
Switch
Position Setting
Function
1
ON
Reverts to attention string of
@ and switches to factory
defaults when reset or re-
powered.
OFF
Maintains user-set attention
upon reset.
2
ON
Limits port name changes and
attention-character changes
to Port 0 only.
OFF
All ports can change port
names and attention
characters.
3
ON
Perform self-test (see
Section 5
)
OFF
Normal operation.
4
ON
DCD (RTS) passed through.
OFF
DCD (RTS) blocked.
5-8
Reserved for future use.
Port 1
Port 2
Leads Passed
DTE
DTE
Port 1 DCD to Port 2 RTS
Port 2 DCD to Port 1 RTS
DTE
DCE
Port 1 DCD to Port 2 DCD
Port 2 RTS to Port 1 RTS
DCE
DTE
Port 1 RTS to Port 2 RTS
Port 2 RTS to Port 1 DCD
DCE
DCE
Port 1 RTS to Port 2 DCD
Port 2 RTS to Port 1 DCD
3.2 Configuring Shunt Jumpers for DTE or DCE
Each of the five (or nine) ports has a bank of shunt
jumpers located next to its port connector on the
rear of the internal board or boards. (See Fig. 1 for
their location.) These jumpers allow each port to be
configured as either Data Terminal Equipment
(DTE) or Data Communications Equipment
(DCE). You don’t need a crossover cable to connect
your equipment to the Code Operated Matrix
Switch—just standard straight-through cabling.
Shunt jumpers are fragile. When removing them,
use a small flathead screwdriver or IC remover. With
a screwdriver, use a gentle motion, prying from one
end of the shunt. When installing, press down
gently only after you have made sure all pins are
above holes.
Table 3. Input and Output Signals
Table 4. DIP Shunt Settings
NOTE: If you use a cross-pinned cable, set the DIP
shunt setting to the opposite of the one
recommended above.
Connecting straight cable to:
Set DIP Shunt to:
PC w/25-pin connector
DCE
DEC™ computer
DCE
Data General computer
DCE
Most printers (ex: HP
®
LaserJet
®
)
DCE
DTE devices
DCE
Modem
DTE
HP minicomputer
DTE
DCE devices
DTE
Signal Pin Direction as DTE Direction as DCE
TXD
2
Output
Input
RXD
3
Input
Output
RTS
4
Output
Input
CTS
5
Input
Output
DSR
6
N/A
Output
DCD
8
Input
Output
DTR
20
Output
Input
RI
22
Input
N/A
