Cooper Instruments & Systems DFI 1650 Multi-Channel Digital Force Indicator - Manual (Page 25)

CF 66 19 Rev. C 2/05
7.2 Wiring
The System connector on the instrument’s rear panel is used, among other things, for serial communications. See
“System Connector”, Chapter 5, for wiring information.
All of the serial communications pins on the 25-pin System connector have 500V of electrical isolation from all other
pins and connectors on the instrument. Additionally, all serial communications pins are protected against
electrostatic discharge (ESD).
7.3 Communications Protocol
7.3.1 RS-232 vs. RS-485
DFI instruments are available with either of two communications protocols, RS-232 or RS-485. Only one of these
can be installed at a time at the factory.
RS-232 provides for only one receiver and transmitter per loop, and a loop length of no more than 50 feet.
RS-485 allow up to 32 devices per loop, and a loop length of no more than 4000 feet. All devices receive
messages in parallel on the line, the so-called “multi-drop” system. To avoid garbled transmissions, only one
device should respond to a particular message. Therefore, every device on the loop must have a unique address.
If you have an instrument with more than one channel, transmission must be addressed to the appropriate channel
within the instrument.
7.3.2 Parameters
All DFI instruments use no parity, 8 data bits, and 1 stop bits (“N, 8, 1”) for serial communications. Baud rates
available are 300, 600, 1200, 2400, 4800, 9600, 19200 and 38400. As shipped from the factory, all instruments are
set at 9600 baud. The baud rates are selected via the RS-232 or RS-485 and not through the front panel.
7.4 Serial Com. Menu
7.4.1 Overview
The Serial Com menu allows you to examine the settings for serial communications as well as test the
communications link. You cannot change the settings for serial communications through the menus; these settings
can only be changed via serial communications.
Detailed instructions on operating the DFI instrument in the SETUP Menu mode can be found in “SETUP Menu
mode”. A diagram of all menus is located in “Setup Menu Reference in Chapter 18”.
7.4.2 INTERFACE Menu Item
This menu item indicates which serial communications interface is installed in the instrument: “RS-232” or “RS-
485”.
7.4.3 ADDRESS Menu Item
This allows you to examine the two-character address that the instrument will respond to. The default address of
“00” (ASCII codes decimal 30, decimal 30). Please see the “DFI 1550/1650 Communications Guide” for
information on using the “W4” command to change the address.
7.4.4. BAUD RATE Menu Item
This allows you to examine the baud rate that the instrument uses for serial communications. The default baud rate
is 9600. Please see the “DFI 1550/1650 Communications Guide” for information on using the “W1” command to
change the baud rate.
7.4.5 AUTO LINE-FEED Menu Item
This allows you to examine the setting (on/off) of the auto line-feed function. When set to “on”, a line-feed
character (ASCII code decimal 10) is transmitted just before the carriage return (ASCII code decimal 13) that
signifies the end of the instrument’s response.
The default setting is “on”.