25
StarPac Intelligent Control System FCD VLENIM0066-02 02/10
flowserve.com
®
11.4 Selecting Correct Modbus Transmission Mode
Two transmission modes exist in a Modbus system, ASCII and RTU (default). Use the ASCII mode when transmitting
information through a device that uses ASCII control codes; for example, a modem. When ASCII mode is used, Parity
must be set to None. Use the RTU mode when connecting directly to both devices; for example, an RS-485 interface card
wired directly to a StarPac 3 system.
If the default Modbus transmission mode setting needs to be changed, use the ‘Comm Port’ option in the configuration
menu of the local keypad interface to change the settings.
11.5 Selecting Proper RS-485 Termination Resistor Setting
A termination resistor must be installed on the two most remote devices on the network, counting the host computer as
any other device.
(For example, a single 3 unit and the RS-485 driver in the host computer would each require the termination resistor
to be installed. If four units were on the network with a host computer, decide which of the two devices have the most
combined cable length between them. These two devices should have the termination resistors installed. The termi-
nation resistors should be disabled in the devices not considered to be the most remote using the instructions in the
next section. Using more than two termination resistors in a network can cause the RS-485 communications to operate
erratically or fail).
On the top electronic board there are two termination jumpers for the RS-485 communications to the right of the LCD
display. The jumper labeled JP1 enables the termination resistor for Com A and the jumper labeled JP2 enables the
termination resistor for Com B. To enable 120 ohms termination, insert both jumpers for A and B channels. To disable
termination, remove both jumpers from each channel.
11.6 Communication Port B
Com Port B can be set for the following three configurations;
• RS-485
• USB
• Infrared
1.
When RS-485 is selected, the StarPac 3 device will need to be wired correctly. Refer to Figure 6 and Table IX
for wiring connection instructions. Follow the instructions as outlined in sections 11.2 to 11.5 to configure
Com Port B.
2.
When a 2.0 mini-B USB cable is plugged into the StarPac 3 on the Customer Interface Board, Com Port B
will automatically be configured for communication through the USB cable. The baud rate will automatically
be set to 57600. When using StarTalk XP, make sure the computer com port baud rate setting is also set to
57600.
3.
When Infrared is selected, the StarPac 3 will be able to receive communication through the glass on the main
cover. It is not necessary to remove the main cover. Communication will need to occur using a PDA with
special software. The software will contain a keypad simulator that will have the same functionality as the
local keypad.
