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Chapter 2 Hardware Overv iew of the NI 78x x Multifunction Reconfigur able I/O User Manual 2-4 ni.com NI 7831/7833 Over view The NI 7831/7833 each have eight inde pendent, 16-bit AI channels; eight independent, 16-bit AO…
Chapter 2 Hardware Overview of the NI 78xx
© National Instruments Corporation 2-3 Multifunction Reconfigurable I/O User Manual
Figure 2-3. NI 7831/7833/784x/785x Block Diagram
NI 7811 Overview
The NI 7811 has 160 bidirectional DIO lines and a Virtex-II XC2V1000
FPGA.
NI 7813 Overview
The NI 7813 has 160 bidirectional DIO lines and a Virtex-II XC2V3000
FPGA.
NI 7830 Overview
The NI 7830 has four independent, 16-bit AI channels; four independent,
16-bit AO channels; 56 bidirectional DIO lines that you can configure
individually for input or output; and a Virtex-II XC2V1000 FPGA.
+
AI+
AI–
PCI/PXI/CompactPCI Bus
Input Mux
Instrumentation
Amplifier
Input Mode Mux
AISENSE
AIGND
16-Bit
DAC
x8 Channels
2
x8 Channels
Configuration
Flash
Memory
User-
Configurable
FPGA on RIO
Devices
Bus
Interface
Connector 1 (DIO)Connector 2 (DIO)
Data/Address/
Control
Digital I/O (16)
Digital I/O (40)
Digital I/O (40)
Calibration
DACs
Configuration
Control
Connector 0 (MIO)
Calibration
DACs
Voltage
Reference
–
16-Bit
ADC
Temperature
Sensor
Calibration
Mux
RTSI/PXI Triggers
RTSI Bus
Address/Data
Control
PXI Local Bus (NI PXI-783x only)
Chapter 2 Hardware Overview of the NI 78xx
Multifunction Reconfigurable I/O User Manual 2-4 ni.com
NI 7831/7833 Overview
The NI 7831/7833 each have eight independent, 16-bit AI channels; eight
independent, 16-bit AO channels; 96 bidirectional DIO lines that you can
configure individually for input or output; and a Virtex-II XC2V3000
FPGA.
NI 784x Overview
The NI 784x each have eight independent, 16-bit AI channels;
eight independent, 16-bit AO channels; and 96 bidirectional DIO lines that
you can configure individually for input or output. The PXI-7841 has a
Virtex-5 LX30 FPGA, and the PXI-7842 has a Virtex-5 LX50 FPGA.
NI 785x Overview
The NI 785x each have eight independent, 16-bit AI channels;
eight independent, 16-bit AO channels; and 96 bidirectional DIO lines that
you can configure individually for input or output. The PXI-7851 has a
Virtex-5 LX30 FPGA, the PXI-7852 has a Virtex-5 LX50 FPGA,
the PXI-7853 has a Virtex-5 LX85 FPGA, and the PXI-7854 has a Virtex-5
LX110 FPGA.
Analog Input (NI 783x /784x /785x Only)
You can sample NI 783x/784x/785x AI channels simultaneously or at
different rates. The input mode is software configurable, and the input
range is fixed at ±10 V. The converters return data in two’s complement
format. Table 2-1 shows the ideal output code returned for a given AI
voltage.
Table 2-1. Ideal Output Code and AI Voltage Mapping
Input Description AI Voltage
Output Code (Hex)
(Two’s Complement)
Full-scale range –1 LSB 9.999695 7FFF
Full-scale range –2 LSB 9.999390 7FFE
Midscale 0.000000 0000
Negative full-scale range +1 LSB –9.999695 8001
Chapter 2 Hardware Overview of the NI 78xx
© National Instruments Corporation 2-5 Multifunction Reconfigurable I/O User Manual
Input Modes
The NI 783x/784x/785x input mode is software configurable. The input
channels support three input modes—differential (DIFF), referenced single
ended (RSE), and nonreferenced single ended (NRSE). The selected input
mode applies to all the input channels. Table 2-2 describes the three input
modes.
Input Range
The NI 783x/784x/785x AI range is fixed at ±10 V.
Connecting Analog Input Signals
The AI signals for the NI 783x/784x/785x are AI<0..n>+, AI<0..n>–,
AIGND, and AISENSE. For the NI 7830, n=4. For the NI 7831/7833/
784x/785x, n=8. The AI<0..n>+ and AI<0..n>– signals are connected to the
Negative full-scale range –10.000000 8000
Any input voltage —
Table 2-2. Available Input Modes for the NI 783x/784x/785x
Input Mode Description
DIFF When the NI 783x/784x/785x is configured in DIFF input mode, each channel
uses two AI lines. The positive input pin connects to the positive terminal of the
onboard instrumentation amplifier. The negative input pin connects to the
negative input of the instrumentation amplifier.
RSE When the NI 783x/784x/785x is configured in RSE input mode, each channel
uses only its positive AI pin. This pin connects to the positive terminal of the
onboard instrumentation amplifier. The negative input of the instrumentation
amplifier connects internally to the AI ground (AIGND).
NRSE When the NI 783x/784x/785x is configured in NRSE input mode, each channel
uses only its positive AI pin. This pin connects to the positive terminal of the
onboard instrumentation amplifier. The negative input of the instrumentation
amplifier on each AI channel connects internally to the AISENSE input pin.
Table 2-1. Ideal Output Code and AI Voltage Mapping (Continued)
Input Description AI Voltage
Output Code (Hex)
(Two’s Complement)
Output Code
32,768
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10.0 V×