28
Siemens Building Technologies
Fire Safety & Security Products
10.2008
9 System
integration
9.1
Connecting VK-3 keyboards
You can connect a total of sixteen keyboards to the keyboard serial port of a VIS3I-
328, using a single RS-485 cable 'daisy-chained' between multiple keyboards.
For a single keyboard, keyboard power is drawn from the VIS3I-328. For more than
one keyboard, you need to use a local 12 V DC power supply for each keyboard.
CAUTION
Do not connect a keyboard to a dc power supply as well as wiring to the 12 V
keyboard connector supply, or damage may occur.
RS-485 cable wiring is as follows.
NOTE
The cable screen is grounded at the VIS3I-328 connector shell, and is only linked to the next cable
screen at each keyboard connector.
VIS3I-328
Keyboard Port
Cable
Keyboard 1
RS-422/485 ports
Cable
Keyboard 2 to 16
RS-422/485 ports
Shell
Screen Not
connected
Screen Not
connected
Pin 1 (+12 V)
Pin 1 (+12 V)
Not connected
Pin 6 (0 V)
Twisted
pair
Pin 6 (0 V)
Not connected
Pin 2 (+12 V)
Pin 2 (+12 V)
Not connected
Pin 7 (0 V)
Twisted
pair
Pin 7 (0 V)
Not connected
Pin 5 (data -)
Pin 5 (data -)
Pin 5 (data -)
Pin 9 (data +)
Twisted
pair
Pin 9 (data +)
Twisted
pair
Pin 9 (data +)
Tab. 7
RS-485 keyboard cable wiring
In cases where you need to connect a keyboard via a fibre link, or through some
other device where the short (less than 3 ms) line turnaround requirement of the
Molynx protocol is a problem, you can connect a single keyboard using an RS-422
cable as follows. (The +12 V and 0 V connections are not required if the keyboard
has its own DC power supply.)
VIS3I-328
Keyboard Port
Cable
Keyboard 1 RS-422/485
port
Shell Screen
Not
connected
Pin 1 (+12 V)
Pin 1 (+12 V)
Pin 6 (0 V)
Twisted
pair
Pin 6 (0 V)
Pin 2 (+12 V)
Pin 2 (+12 V)
Pin 7 (0 V)
Twisted
pair
Pin 7 (0 V)
Pin 4 (data T-)
Pin 5 (data R-)
Pin 8 (data T+)
Twisted
pair
Pin 9 (data R+)
Pin 5 (data R-)
Pin 4 (data T-)
Pin 9 (data R+)
Twisted
pair
Pin 8 (data T+)
Tab. 8
RS-422 keyboard cable wiring
For more details of keyboard cabling, refer to the Keyboard User Manual.