User`s guide

46 • Operation Theory
4.3 Extended Digital I/O Port
There are 4 extended digital input (EDI) signals and 4 extended digital output
(EDO) signals on CN3 connector. The 4 EDI signals are dedicated used as
input signal, however the 4 EDO signals can be used as digital input (Mode 1),
digital output (Mode 2) or channel number output (Mode 3).
For power on safety, the EDO channel is set to be input when power on initial.
To modify the configuration of the usage of the signals, please use the
“_9111_Set_EDO_Function” in the library.
Note that when set the EDO function as channel number output (Mode 3), it
presents the high nibble (4 MSBs) of the channel number no matter manual
scan or auto scan mode.
4.4 D/A Conversion
The PCI-9111 has one analog output channel. The signal range can be
uni-polar or bi-polar which is set by JP1.
To D/A Output
D/A Converter
-
+
-
10V
Ref In
Analog GND
Pin
-
30 (DA Out)
Figure 14. D/A Conversion Circuit
The operation of the D/A conversion is much simpler than the A/D operation.
You only need to write a digital value into the D/A data registers and the
corresponding voltage will be outputted on DAOut (pin-30 of CN3). Refer to
section 3.16 for information about the D/A data registers. The mathematical
relationship between the digital data DAn and the output voltage is formulated
as follows:
V
out
=span x DAn / 4096– Unipolar
V
out
=span x DAn / 4096 + (-10)– Bipolar
Where span is the span in volts. If your output range is -10V~10V (Bipolar),
then span is 20; if your output range is 0~10V (Unipolar), then span is 10. The
V
out
is the output voltage, and the DAn is the digital data value in the D/A data
registers.