Cooper Instruments & Systems DFI 1650 Multi-Channel Digital Force Indicator - Manual (Page 12)

CF 126 9 Nov 2001
The RS-485 communications pins are electrically isolated from the rest of the instrument.
The RS-232 and RS-485 interfaces are exclusive; an instrument cannot have both.
5.4 RS-422 Wiring
RS-422 uses two pairs of wires to communicate between one bus master and up to 10 slave devices. It is
a full-duplex system, i.e. the bus master can transmit and receive data from the slaves at the same time.
Model DFI Model DFI Controller
DDB-25 connector DB-25 connector RS-422
Slave Slave Bus Master
Figure 5-1:RS-422 Wiring
5.5 RS-485 Wiring
An RS-485 balanced differential communications bus uses one pair of wires to allow up to 32 devices to
send and receive data. A two-wire RS-485 system is a half-duplex system, which means that no device
can transmit and receive data at the same time, and that only one device can "drive" or "talk" on the bus
at a time. An SC Instrument is configured as a two-wire RS-485 device when "Transmit (+)" (pin 13) is
connected to "Receive (+)" (pin 25), and "Transmit (-)" (pin 12) and "Receive (-)" (pin 24) are connected
together.
Model DFI Model DFI Controller
DB-25 connector DB-25 connector RS-485
Slave Slave Bus Master
Figure 5-2: RS-485 Wiring
5.6 Addressing
Every DFI instrument on the RS-422/RS-485 communications bus must have a unique 2-character
address. Each instrument as shipped from the factory has its address set at "00" (i.e. ASCII code 30
decimal, 30 decimal).