Product Introduction
The NI PCIe-8431/16 is a high-performance 16-port RS-485/RS-422 serial interface device designed for industrial communication, automated test, instrument control, production systems, laboratory automation, and integration of multiple serial devices.
The PCIe-8431/16 combines 16 independent serial ports with a PCI Express host interface and supports communication rates up to 3 Mb/s. It supports both RS-485 and RS-422 communication and provides selectable 2-wire and 4-wire transceiver modes for half-duplex and full-duplex applications.
With high-performance DMA transfers, multithreading, and multiprocessor support, the PCIe-8431/16 is particularly suitable for applications that require simultaneous communication with many industrial or test devices.
Product Overview
The National Instruments PCIe-8431/16 provides a high-density serial communication solution for computers equipped with a compatible PCI Express slot.
A typical architecture is:
Host Computer → PCI Express → PCIe-8431/16 → RS-485 / RS-422 → Instruments / Controllers / DUTs
Instead of installing multiple low-port-count serial interfaces, the PCIe-8431/16 provides up to 16 serial channels from a single PCI Express card.
Key Features
16 Serial Communication Ports
The PCIe-8431/16 provides 16 serial channels, making it suitable for systems that need to communicate with many external devices simultaneously.
Typical connected equipment can include:
- Industrial controllers
- PLCs
- Test instruments
- Embedded controllers
- Motion-control equipment
- Sensors
- Barcode readers
- Production equipment
- Data acquisition equipment
RS-485 Support
The PCIe-8431/16 supports RS-485, a differential serial communication standard widely used in industrial environments.
RS-485 is particularly suitable for applications requiring:
- Longer communication distances
- Improved noise immunity
- Industrial environments
- Multi-device communication
- Differential signaling
RS-422 Support
In addition to RS-485, the PCIe-8431/16 supports RS-422 serial communication.
This allows the same interface family to communicate with equipment using either RS-485 or RS-422 electrical standards.
Simultaneous RS-485 and RS-422 Operation
Compatible ports on the PCIe-8431/16 can be used for RS-485 and RS-422 communication simultaneously.
For example:
Selected Ports → RS-485 Devices
Other Ports → RS-422 Devices
This provides additional flexibility when a test or automation system contains equipment using different serial standards.
Up to 3 Mb/s Communication
The PCIe-8431/16 supports serial communication rates from low baud rates up to a maximum of 3 Mb/s under supported operating modes.
This makes the device suitable for applications requiring significantly higher throughput than conventional low-speed serial interfaces.
2-Wire RS-485 Mode
The PCIe-8431/16 supports 2-wire RS-485 communication.
A 2-wire configuration commonly uses the same differential pair for transmitting and receiving data and is therefore typically associated with half-duplex communication.
4-Wire Communication Mode
The device also supports 4-wire transceiver configurations.
Separate differential pairs can be used for transmit and receive operations, allowing full-duplex communication in compatible systems.
Full-Duplex Communication
The PCIe-8431/16 supports compatible full-duplex serial communication configurations.
Full-duplex operation allows transmission and reception to occur simultaneously when the connected device and wiring architecture support it.
Half-Duplex Communication
The device also supports half-duplex communication, commonly used in 2-wire RS-485 networks.
In this architecture, connected devices share the communication pair and coordinate when each device transmits.
High-Performance DMA Transfers
The PCIe-8431/16 uses high-performance DMA transfers to efficiently transfer serial data between the interface hardware and host computer.
DMA-based transfer architecture can reduce processor overhead compared with communication methods that require more direct CPU involvement.
Multithreading Support
The PCIe-8431/16 supports multithreaded applications, which is particularly valuable when multiple serial ports are communicating simultaneously.
Different application threads can manage different communication tasks as part of a larger automated test or industrial control application.
Multiprocessor Support
The interface architecture also supports multiprocessor systems, helping high-channel-count serial applications take advantage of modern host-computer architectures.
Standard COM Port Compatibility
NI serial interfaces appear as standard COM ports to compatible software.
This can simplify integration with existing applications that already communicate through standard serial ports.
A typical application architecture is:
Application Software → COM Port → NI Serial Driver → PCIe-8431/16 → RS-485 / RS-422 Device
PCI Express Host Interface
The PCIe-8431/16 uses a PCI Express x1 host interface.
It can be installed in compatible desktop, workstation, rackmount, or industrial computers with an appropriate PCI Express expansion slot.
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Type | Serial Interface Device |
| Model | PCIe-8431/16 |
| Manufacturer | National Instruments |
| Part Number | 780592-02 |
| Host Interface | PCI Express x1 |
| Serial Channels | 16 |
| Supported Serial Protocols | RS-485 / RS-422 |
| Maximum Baud Rate | 3 Mb/s |
| Minimum Supported Baud Rate | 2 Baud |
| Transceiver Modes | 2-Wire and 4-Wire |
| Communication Modes | Half-Duplex / Full-Duplex |
| Isolation | Non-Isolated |
| Serial Connectors | 2 × 68-Pin VHDCI |
| External Port Connection | 16 × DB-9 Through Included Breakout Cables |
| DMA | Supported |
| Multithreading | Supported |
| Multiprocessor Support | Supported |
| Software Interface | Standard COM Port / NI-Serial |
| Weight | Approximately 101 g |
| Dimensions | 11.12 × 17.53 cm |
| Primary Applications | Industrial Serial Communication, Automated Test, Instrument Control and System Integration |
How Does the PCIe-8431/16 Work?
The PCIe-8431/16 provides the electrical and communication interface between software running on the host computer and external RS-485 or RS-422 devices.
For transmitted data:
Application → COM Port / NI-Serial → PCIe-8431/16 → RS-485 / RS-422 → External Device
For received data:
External Device → RS-485 / RS-422 → PCIe-8431/16 → Driver → Application
Each port can be used to exchange commands, measurement data, status information, control messages, and other serial data with compatible external equipment.
16-Port Serial Architecture
High port density is one of the primary advantages of the PCIe-8431/16.
The device uses two high-density 68-pin VHDCI connectors. Breakout cables convert these connections into standard DB-9 serial connectors.
A simplified configuration is:
VHDCI Connector 1 → Ports 1–8
VHDCI Connector 2 → Ports 9–16
This architecture allows 16 external serial devices to be connected while keeping the PCI Express board itself compact.
Included Breakout Cables
The PCIe-8431/16 kit includes two 1-meter 68-pin VHDCI-to-eight-DB-9 serial cables.
Each breakout cable converts one high-density connector into eight individual serial connections.
Together:
2 Breakout Cables × 8 Ports = 16 Serial Ports
When purchasing a replacement or used PCIe-8431/16, confirm whether the required breakout cables are included.
RS-485 Communication
RS-485 uses differential signaling and is widely used in industrial environments because it provides good noise immunity and supports communication architectures involving multiple devices.
Typical RS-485 applications include:
- Industrial automation
- Process equipment
- Machine control
- Distributed sensors
- Production equipment
- Building automation
- Test-system communication
RS-422 Communication
RS-422 also uses differential signaling and is commonly used for reliable serial communication over longer distances than conventional RS-232.
The PCIe-8431/16 supports RS-422 in addition to RS-485, allowing the device to integrate with a broad range of industrial and test equipment.
RS-485 vs RS-422
| Feature | RS-485 | RS-422 |
|---|---|---|
| Signaling | Differential | Differential |
| Multi-Device Networks | Well Suited | More Limited |
| 2-Wire Operation | Common | Typically 4-Wire |
| Half-Duplex | Common | Application Dependent |
| Full-Duplex | Supported with Appropriate Wiring | Common |
| Differential Noise Immunity | High | High |
2-Wire vs 4-Wire RS-485
| Feature | 2-Wire | 4-Wire |
|---|---|---|
| Data Pairs | 1 Differential Pair | Separate TX and RX Pairs |
| Typical Communication | Half-Duplex | Full-Duplex |
| Wiring Complexity | Lower | Higher |
| Simultaneous TX/RX | No | Yes |
The correct mode should be selected according to the communication architecture and wiring requirements of the connected equipment.
Important Note About 2-Wire Auto Control
Although the PCIe-8431/16 supports a maximum serial rate of 3 Mb/s, the maximum rate for 2-wire automatic RS-485 transceiver control mode is 2 Mbaud.
This distinction should be considered when designing high-speed 2-wire RS-485 systems.
Industrial Automation Applications
The PCIe-8431/16 is well suited for industrial automation systems requiring communication with multiple serial devices.
For example:
Industrial PC → PCIe-8431/16 → Multiple RS-485 Controllers / Sensors / Machines
The high port count can simplify system architecture by consolidating many serial connections onto a single PCI Express interface.
Automated Test Applications
The PCIe-8431/16 can integrate serial instruments and DUTs into automated test systems.
A typical automated test platform may include:
- PCIe-8431/16 serial interface
- DAQ devices
- Oscilloscopes or digitizers
- Programmable power supplies
- Electronic loads
- Switch systems
- Digital I/O
- Test fixtures
The host application can coordinate communication with multiple serial devices while performing measurements and automated test sequences.
Instrument Control
Compatible instruments using RS-485 or RS-422 can be controlled through the PCIe-8431/16.
Typical operations include:
- Sending configuration commands
- Starting measurements
- Reading measurement results
- Monitoring instrument status
- Changing operating parameters
- Logging serial data
Multi-Device Communication
The 16-port architecture allows one computer to manage many independent serial connections.
For example:
Port 1 → Controller
Port 2 → Sensor System
Port 3 → Motion Controller
Port 4 → Test Instrument
Ports 5–16 → Additional Serial Equipment
This can significantly reduce the number of separate communication adapters required in complex systems.
RS-485 Network Termination
Proper termination is important for reliable RS-485 communication, particularly at higher communication rates and longer cable lengths.
Before commissioning a network, verify:
- Termination resistance
- Biasing requirements
- Cable impedance
- Network topology
- Cable length
- Communication rate
- Number of connected devices
Incorrect termination can cause reflections, communication errors, intermittent data loss, or complete communication failure.
RS-485 Biasing
RS-485 networks may require bias resistors to establish a known bus state when no transmitter is actively driving the network.
Biasing should be configured according to the network topology, termination arrangement, connected devices, and application requirements.
High-Speed Serial Communication
The PCIe-8431/16 supports rates up to 3 Mb/s, making it suitable for higher-throughput serial applications.
However, reliable communication depends on the complete system, including:
- Baud rate
- Cable length
- Cable quality
- Termination
- Network topology
- Electrical noise
- Connected transceivers
- Wiring quality
Maximum theoretical interface speed does not guarantee reliable operation at that rate under every physical network condition.
DMA-Based Data Transfer
The PCIe-8431/16 supports high-performance Direct Memory Access (DMA).
DMA allows serial data to be transferred efficiently between hardware and host memory, which can be valuable when many ports are simultaneously transmitting and receiving data.
Standard COM Port Operation
NI serial interfaces appear as standard COM ports in compatible operating systems.
This means many existing applications designed for standard serial communication can access the PCIe-8431/16 without requiring a completely proprietary communication architecture.
The exact COM port numbers assigned by the operating system can vary according to system configuration.
NI-Serial Driver
The PCIe-8431/16 uses compatible NI-Serial software for serial interface configuration and operation.
The driver provides the software layer required for the host operating system and application software to access the serial ports.
Driver and operating-system compatibility should always be verified before installing the device into an existing system.
LabVIEW Integration
The PCIe-8431/16 can be integrated into compatible LabVIEW applications for industrial communication, automated testing, device control, and data logging.
Typical applications include:
- Serial instrument control
- Automated production testing
- Industrial device monitoring
- Multi-port data acquisition
- Serial data logging
- Equipment configuration
NI-VISA Integration
Compatible serial applications can use NI-VISA for communication with serial devices.
A typical VISA workflow is:
VISA Open → Configure Serial Port → VISA Write → VISA Read → VISA Close
This approach is commonly used when controlling serial instruments through LabVIEW or other supported development environments.
PCIe-8431/16 vs PCIe-8430/16
The PCIe-8431/16 and PCIe-8430/16 provide the same high-density 16-port architecture but support different serial electrical standards.
| Feature | PCIe-8431/16 | PCIe-8430/16 |
|---|---|---|
| Serial Standard | RS-485 / RS-422 | RS-232 |
| Ports | 16 | 16 |
| Maximum Baud Rate | 3 Mb/s | 1 Mb/s |
| Differential Signaling | Yes | No |
| Multi-Device Industrial Networks | Better Suited | Point-to-Point Applications |
| Host Interface | PCI Express | PCI Express |
The serial electrical standard required by the external equipment should be the primary selection criterion.
PCIe-8431/16 vs PCIe-8431/8
| Feature | PCIe-8431/16 | PCIe-8431/8 |
|---|---|---|
| Serial Standard | RS-485 / RS-422 | RS-485 / RS-422 |
| Serial Ports | 16 | 8 |
| Maximum Baud Rate | 3 Mb/s | 3 Mb/s |
| Host Interface | PCI Express | PCI Express |
| Best Application | High Port Count Systems | Medium Port Count Systems |
PCIe-8431/16 vs PXIe-8431/16
The primary difference between these devices is the host platform.
| Feature | PCIe-8431/16 | PXIe-8431/16 |
|---|---|---|
| Serial Protocol | RS-485 / RS-422 | RS-485 / RS-422 |
| Ports | 16 | 16 |
| Maximum Baud Rate | 3 Mb/s | 3 Mb/s |
| Host Platform | PCI Express PC | PXI Express Chassis |
| Typical Installation | Industrial / Desktop PC | Modular PXIe Test System |
PCIe-8431/16 vs Isolated Serial Interface
The PCIe-8431/16 is a non-isolated serial interface.
For systems where electrical isolation between the computer and serial network is required, an appropriate isolated NI serial interface should be considered.
Isolation can be particularly important when:
- Ground potential differences are present
- Electrical noise is severe
- Equipment is distributed over large installations
- Ground loops are a concern
- Additional electrical protection is required
PCIe-8431/16 vs USB RS-485 Adapter
| Feature | PCIe-8431/16 | Typical USB RS-485 Adapter |
|---|---|---|
| Installation | Internal PCI Express | External USB |
| Ports | 16 | Usually Fewer |
| Maximum Rate | Up to 3 Mb/s | Device Dependent |
| DMA | High-Performance DMA | Device Dependent |
| Permanent Test-System Integration | Well Suited | Application Dependent |
Legacy System Replacement
The PCIe-8431/16 can be useful when maintaining or upgrading existing industrial and automated test systems that rely on RS-485 or RS-422 communication.
Before replacing another serial interface, verify:
- RS-485 or RS-422 requirement
- Number of required serial ports
- 2-wire or 4-wire operation
- Half-duplex or full-duplex communication
- Required baud rate
- Isolation requirements
- Connector and cable configuration
- Network termination
- Bias resistor requirements
- Available PCI Express slot
- NI-Serial driver compatibility
- Operating system compatibility
- Existing application software
How to Choose an RS-485/RS-422 Interface
Before selecting the PCIe-8431/16, determine:
- Required serial protocol
- Required number of ports
- Maximum baud rate
- 2-wire or 4-wire configuration
- Half-duplex or full-duplex requirement
- Network topology
- Cable length
- Termination requirements
- Biasing requirements
- Electrical isolation requirements
- Host computer interface
- Driver and operating-system compatibility
Industries
- Industrial Automation
- Automated Test
- Electronic Manufacturing
- Production Test
- Laboratory Automation
- Process Control
- Machine Automation
- Research and Development
- Transportation
- System Integration
Applications
Industrial Automation
The PCIe-8431/16 provides high-density RS-485 and RS-422 connectivity for industrial controllers, sensors, machines, and automation equipment.
Automated Test
Sixteen independent serial channels can integrate multiple instruments and DUT interfaces into a single automated test platform.
Instrument Control
Compatible RS-485 and RS-422 instruments can be configured, controlled, and monitored through the PCIe-8431/16.
Production Test
Production systems can communicate with multiple serial DUTs, fixtures, controllers, and supporting equipment from a single host computer.
Multi-Port Data Logging
The 16-port architecture is suitable for applications that need to collect serial data from multiple independent devices.
Legacy Equipment Integration
Existing RS-485 and RS-422 equipment can be integrated into PCI Express-based computers without replacing the external serial devices.
Recommended Related Products
| PCIe-8431/16 | 16-port PCI Express RS-485/RS-422 interface for high-density industrial serial communication. |
| PCIe-8431/8 | 8-port RS-485/RS-422 PCI Express interface for applications requiring fewer serial channels. |
| PCIe-8430/16 | 16-port PCI Express RS-232 interface for high-density RS-232 communication. |
| PXIe-8431/16 | 16-port PXI Express RS-485/RS-422 interface for modular automated test systems. |
| PCI-8433/4 | Isolated RS-485/RS-422 serial interface for applications requiring electrical isolation. |
Why Choose PCIe-8431/16?
- 16 independent serial channels
- RS-485 communication
- RS-422 communication
- Up to 3 Mb/s maximum baud rate
- 2-wire transceiver mode
- 4-wire transceiver mode
- Half-duplex communication
- Full-duplex communication
- High-performance DMA transfers
- Multithreading support
- Multiprocessor support
- Standard COM port compatibility
- PCI Express x1 interface
- High-density serial communication
- Suitable for industrial automation
- Suitable for automated test
- Suitable for instrument control
- Suitable for production test
Frequently Asked Questions
What is the NI PCIe-8431/16?
The NI PCIe-8431/16 is a 16-port PCI Express serial interface device designed for high-speed communication with RS-485 and RS-422 equipment.
What is the part number of PCIe-8431/16?
The PCIe-8431/16 is available under part number 780592-02.
How many serial ports does PCIe-8431/16 have?
The PCIe-8431/16 provides 16 serial channels.
Does PCIe-8431/16 support RS-485?
Yes. RS-485 is one of the primary serial communication standards supported by the PCIe-8431/16.
Does PCIe-8431/16 support RS-422?
Yes. The PCIe-8431/16 supports both RS-485 and RS-422.
Can PCIe-8431/16 use RS-485 and RS-422 at the same time?
Yes. Compatible ports can use RS-485 and RS-422 simultaneously, allowing different ports on the same card to communicate with equipment using the two standards.
What is the maximum baud rate of PCIe-8431/16?
The maximum supported serial communication rate is 3 Mb/s. The 2-wire automatic RS-485 transceiver-control mode has a maximum rate of 2 Mbaud.
Does PCIe-8431/16 support 2-wire RS-485?
Yes. The device supports selectable 2-wire and 4-wire transceiver configurations.
Does PCIe-8431/16 support full-duplex communication?
Yes. The PCIe-8431/16 supports compatible full-duplex and half-duplex communication configurations.
Is PCIe-8431/16 isolated?
No. The PCIe-8431/16 is a non-isolated RS-485/RS-422 serial interface. If electrical isolation is required, select an appropriate isolated serial interface.
What connectors does PCIe-8431/16 use?
The card has two 68-pin VHDCI connectors. Breakout cables convert these connections into 16 individual DB-9 serial ports.
Are breakout cables included with PCIe-8431/16?
NI lists two 1-meter 68-pin VHDCI-to-eight-DB-9 cables with the PCIe-8431/16 device package, providing access to all 16 serial ports.
Does PCIe-8431/16 appear as standard COM ports?
Yes. NI serial interfaces appear as standard COM ports for compatibility with applications that use conventional serial communications.
Can PCIe-8431/16 be used with LabVIEW?
Yes. The PCIe-8431/16 can be integrated into compatible LabVIEW applications for serial communication, instrument control, automated testing, and data logging.
What is the difference between PCIe-8431/16 and PCIe-8430/16?
The PCIe-8431/16 supports RS-485 and RS-422 with rates up to 3 Mb/s, while the PCIe-8430/16 is designed for RS-232 communication with a lower maximum baud rate.
What is the difference between PCIe-8431/16 and PXIe-8431/16?
The primary difference is the host platform. PCIe-8431/16 installs in a PCI Express computer, while PXIe-8431/16 is designed for installation in a PXI Express chassis.
What should I check before purchasing PCIe-8431/16?
Verify the RS-485/RS-422 protocol requirement, required number of ports, baud rate, 2-wire or 4-wire configuration, half-duplex or full-duplex operation, isolation requirements, cable and connector configuration, termination and biasing requirements, available PCI Express slot, NI-Serial driver compatibility, operating system, and existing application software.
Conclusion
The NI PCIe-8431/16 16-Port RS-485/RS-422 Serial Interface Device provides high-density industrial serial connectivity through a PCI Express interface. With 16 channels, communication rates up to 3 Mb/s, selectable 2-wire and 4-wire modes, full- and half-duplex operation, DMA transfers, multithreading, multiprocessor support, and standard COM port compatibility, it is particularly suitable for industrial automation, automated test, instrument control, production systems, multi-device communication, and legacy RS-485/RS-422 equipment integration.
