©
National Instruments Corporation
4-1
80188EB-Based Fieldbus Round Card User Manual
Chapter
4
Interfacing to Your
Round Card
This chapter describes how to connect the Fieldbus Round Card to any
external electronics, and how to develop your Field Device application
to interface to the NI-FBUS Function Block Shell.
Interfacing to the Hardware
The 2
×
4 female connector on the bottom side of the Fieldbus Round
Card, W2, is a user electronics connector that contains signals you can
connect to any user-supplied electronics. There are three sets of signals:
3VOUT, Serial Port 0, and Serial Port 1.
The three sets of signals have a common ground pin. See the W2 item
in Figure 2-2, Bottom Side of 80188EB-Based Fieldbus Round Card, in
Chapter 2, Hardware Installation, for the pinout of the user electronics
connector.
The signals are described as follows:
•
3VOUT—The Fieldbus Round Card has a 3.9 V at 8 mA output
that you can use to power the user electronics.
To activate the 3.9 V output on the W2 connector of the Round
Card, place a 0
Ω
resistor on R18 and replace R35 with a 0
Ω
resistor. Doing this increases the current draw from the Fieldbus to
32 mA in the quiescent state. R18 and R35 are located on the
bottom side of the Round Card.
•
Serial Port 0—The Transmit and Receive pins of the
microprocessor serial port 0 are available at the user electronics
connector. You can use this port as an asynchronous serial link to
the user electronics board. This port can perform interrupt-driven
serial communication. The 3O pin is the Transmit pin and the 3I pin
is the Receive pin. Both of these pins provide 3 V-compatible
signals.
•
Serial Port 1—The Transmit and Receive pins of the processor
serial port 1 are available at the user electronics connector. This
port cannot perform interrupt-driven serial communication. The
