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The 1794 FLEX I/O vs FLEX 5000

1794 FLEX I/O and FLEX 5000 are distributed I/O systems from Allen-Bradley/Rockwell Automation. They are flexible modular systems that provide different functionalities and features in their modules. They are designed and built as cost-effective solutions to provide higher performance and flexible architecture, that eliminates multiple long wiring connections and space requirements while substantially reducing downtime especially for applications where uptime is critical. The new 5094 Flex in the 5000 I/O product line is an upgrade of Rockwell Automation’s highly successful 1794 Flex I/O system. This article provides you with a factual and categorical comparison of the two I/O Distribution systems, to assist you to make the best choice based on the requirements and application of your control system.

1794 FLEX™ I/O Module & FLEX 5000™ I/O Module

Environmental Specifications and Safety Certifications

1794 FLEX I/O

The 1794 FLEX I/O modules operate in a temperature range of 0oC to 55 oC (32 oF to 131 oF). However, these modules are also available with an XT version, which provides operating temperatures of -20oC to 70oC (-4oF to 158oF). Their storage temperatures range between 40oC to 85 oC (-40 oF to 185 oF). While their Relative Humidity in both operating and storage conditions is 5% to 95% non-condensing. The 1794 FLEX I/O systems have a non-operating shock limit of 50 g peak acceleration and 11(±±) ms pulse width.  

They can only withstand an operating shock of 30g peak acceleration and 11(±±) ms pulse width. Their operational Vibration tolerance is 5g RMS tested at 10Hz to 500Hz as per IEC 68-2-6 standards. Also, 1794 FLEX I/O systems are certified with the CE, SIL2, ODVA, UL, C-Tick and ATEX standards.  

FLEX 5000 Series

FLEX 5000 I/O modules operate in a temperature range of -40oC to 70oC (-40 oF to 158 oF). They can be stored in temperature conditions of -40oC to 85 oC (-40oF to 185oF). Their non-operating shock limit is 30g and they can only withstand a maximum 30g shock while in operation. Relative Humidity requirements are 5% to 95%. Their operational vibration tolerance is 5g* RMS, tested at 10Hz to 500Hz with a displacement of 0.030 inches (pp).

They are certified for operation in hazardous areas categorized as Class 1, Zone 2, Div.2 and Groups A, B, C, D. They are also certified for extreme and corrosive environments categorized as Class G1, and ANSI/ISA S71.04 G2, with FLEX 5000 I/O-XT version adding a conformal coating of ANSI/ISA S71.04 G3 rated up to Class G3. They also provide a broad portfolio of discrete fail-safe FLEX 5000 Safety I/O modules, certified up to SIL3, PLE, and CAT.4. Their available certifications include CE, Ex, KC, IECEx, RCM, and c-UL-us.


Both FLEX 5000 and 1794 FLEX I/O are rugged in nature, with their XT versions having similar operating and storage temperatures, as well as operational vibration tolerance. But the 1794 FLEX I/O series can withstand a higher amount of shock when in a non-operating mode compared to FLEX 5000 series. However, the FLEX 5000 I/O modules are built for use in hazardous areas such as radiation-exposed zones where other modules cannot be used. Also, all modules in the FLEX 5000 series are compatible with ControlLogix-XT™ designed for harsh environment systems, but in the 1794 FLEX series only some special environmentally rated modules can be operated in extreme environments and they require conformal coating. Also, FLEX 5000 systems are more secure and operational safe as they are certified up to SIL 3 while FLEX 1794 systems are certified up to SIL 2.

Communication Adapters

FLEX 5000 Adapters

The FLEX 5000 series consist of several EtherNet/IP Adapters such as 5094-AENTR and 5094-AENTRXT, 5094-AEN2TR, and 5094-AEN2TRXT, 5094-AENSFPR and 5094-AENSFPRXT, as well as 5094-AEN2SFPR and 5094-AEN2SFPRXT. All of the aforementioned adapters support some common EtherNet/IP features including 10 Mbps/100 Mbps/1 Gbps connectivity speed; they are compatible with Logix 5000 controllers with firmware version 31.0 or later; they provide Thermal and Configurable Power Monitoring; and they are fitted with Implicit and Explicit Protected Modes.

Implicit Protected Mode is a security enhancement feature that is automatically triggered when adapter bridges I/O connections are made or when the adapter is a target for the I/O connections. While Explicit Protected Mode is a security enhancement measure that occurs on the FLEX 5000 I/O modules; it assists in preventing an authorized configuration change which can cause unforeseen and unintended changes that could ultimately affect the behavior of the control system. Explicit Protected Mode is supported by FLEX 5000 Adapter firmware revision 2.011 or greater and is triggered whenever a given rotary switches pattern is selected.

The FLEX 5000 adapters also support two types of network redundancy: Parallel Redundancy Protocol (PRP) and Device Level Ring (DLR). In these two modes, all the adapter’s Ethernet ports are used to provide redundant network paths. The PRP network is used with FLEX 5000 adapter Firmware release 4.011 or greater. In DLR redundancy mode, the maximum Packet Per Second(PPS) for the I/O connections for all traffic is 100,000pps. While in PRP mode, the maximum PPS is 50,000pps. Thus, whenever the PRP network redundancy mode is enabled, the maximum possible performance of the EtherNet/IP adapter for I/O connections is affected. The FLEX 5000 adapters support other alternatives to using the rotary switches to set the IP addresses. These alternatives are software like DHCP Server, RSLinx® Classic software, and BOOTP/DHCP EtherNet/IP Commissioning utility. Also, the adapters can be mounted on a compatible steel DIN rail that is zinc-plated and chromate-passivated.

To communicate with Logix controllers and I/O modules, FLEX 5000 Adapters use the CIP (Control Industrial Protocol) Sync and PTP (Precision Time Protocol) network. The CIP Sync mechanism enables them to synchronize clocks between controllers, I/O modules, and other automation devices in your control system with minimal intervention from the user. While the Precision Time Protocol (PTP) is a time-transfer protocol that allows precise synchronization of networks. With PTP it is possible to achieve accuracy within the nanosecond range if hardware-assisted synchronization is used. Note that the only adapter network that supports CIP Sync time synchronization is the Ethernet/ IP network.

In addition, FLEX 5000 EtherNet/IP adapters use Studio 5000 Logix Designer® software Version 31 or greater to configure FLEX 5000 I/O modules. Also, for convenience, these adapters can be used to substitute for other FLEX 5000 adapters connected in Studio 5000®. For instance, if your Studio 5000® design project requires a 5094-AENTR adapter that supports 8 I/O modules, but you only have an adapter that supports 16 I/O modules like a 5094-AEN2TR adapter; then from the 5094-AENTR add-on profile, you can select the compatible mode. This compatibility mode allows you to conveniently use 5094-AEN2TR rather than the 5094-AENTR adapter, without making any changes to your Studio 5000® design project.

Lastly, FLEX 5000 EtherNet/IP adapters with SFP (Small Form-Factor Pluggable) support are available. They include: the 5094-AENSFPRXT, 5094-AENSFPR, 5094-AEN2SFPRXT, and 5094-AEN2SFPR. These adapters support EtherNet network transceiver modules in SFP format. They also support both Copper and Fiber media, while the other FLEX 5000 adapters without SFP support only Copper media. In addition, all firmware versions of SFP FLEX 5000 adapters can support Web server and SNMP enable/ disable the feature; Rotary switches, PRP/DLR switch monitoring, and Explicit Protected Mode, whereas only Firmware revision 2.011 or later of the FLEX 5000 adapters without SFP can support the aforementioned features.

FLEX 1794 Adapters

The 1794 FLEX I/O consists of dual-port EtherNet/IP adapters namely 1794-AENTR and 1794-AENTRXT. The common features for these adapters include: full/half-duplex 100Mbit operation, compatible with Logix 557x controller’s version 20 or later, DIN rail mounting, the same DIN rail can be used for communication to and from other FLEX I/O modules.

Also, they use RSLogix 5000 software version 20 or higher to configure the connected FLEX 1794 I/O modules. And for communication support, they use RSLinx software version 2.59 or later. With FLEX 1794 adapters no routing tables are required and no network scheduling is needed. For EtherNet cable connections, UTP CAT.5 twisted pair cables are used for networks using Ethernet 100baseT and 10baseT.

These adapters use EtherNet/IP messages that are encapsulated within standard TCP/IP/UDP protocols and an open application layer protocol known as the Control and
Information Protocol (CIP). FLEX 1794 Ethernet/IP adapters use Transmission Control Protocol (TCP) to transmit Explicit messages, which encrypt “as-needed” information(data). On the other hand, User Datagram Protocol (UDP) is used where low latency and high-speed are important to transmit Implicit messages, encrypting control data for the 1794 FLEX I/O modules.

The TCP/UDP protocols make it possible for the 1794-AENTRXT and 1794-AENTR adapters to use the Control and Information Protocol (CIP). CIP protocol is message-based and it implements a relative path for sending Explicit and Implicit messages from the producing devices to the consuming devices within the control system. In FLEX 1794 adapters, the CIP is the common application layer protocol specified for the following networks:

  • EtherNet/IP: an open standard industrial network that supports Explicit and Implicit messaging. 1794-AENT adapters have a communication rate of 10/100 Mbps and an I/O module capacity of 8. 
  • ControlNet: allows high-speed and intelligent control devices to exchange information/data required for operator interface, troubleshooting, work-cell coordination, remote device configuration, supervisory control and programming. 1794-ACN15 and 1794-ACNR15 adapters have a communication rate of 5 Mbps and support up to 8 FLEX 1794 I/O modules. 
  • DeviceNet: provides a variety of plant floor devices with high-speed access to plant-floor data and significantly reduces the wiring connections of such devices. 1794-AND adapters have a communication rate of 125Kbps/250Kbps/500Kbps and an I/O module capacity of 8. 

The common application layer supported by FLEX 1794 enables the EtherNet/IP, ControlNet, and DeviceNet networks to connect to the CIP protocol at their upper levels, while at their lower levels they remain media independent. Therefore, FLEX 1794 Adapters give you the flexibility to specify the best network for your application and eliminate the complex and costly gateways required if you are to connect dissimilar upper-level networks.


Both FLEX 1794 Adapters and FLEX 5000 Adapters support DIN rail mounting and the use of BOOTP/DHCP utility and RSLinx® Classic software as additional methods for assigning and changing the IP addresses. But FLEX 1794 adapters offer better network flexibility through the CIP Application Layer protocol which allows open communication on DeviceNet®, ControlNet®, and EtherNet/IP™. This makes the interchangeability and interoperability of control devices on Ethernet/IP networks a reality with FLEX 1794 Adapters, for control applications and advanced industrial automation.

However, to compensate for the lack of network flexibility; the FLEX 5000 Adapters enhance communication with a 1 Gbps EtherNet/IP connectivity through fiber or copper media. The copper or fiber media is only supported by FLEX 5000 SFP adapters which are not available with the FLEX 1794 series. Also, FLEX 5000 adapters support a wide range of network topologies including Star, DRL, Linear, and PRP.

Moreover, their compatibility with Studio 5000 Logix Designer® software, makes the FLEX 5000 adapters more convenient to use. As it is possible to substitute missing adapters in your studio 5000® project with other FLEX 5000 adapters using the compatibility mode in the adapters’ add-on profiles. Whereas with FLEX 1794 adapters, this is only possible with other FLEX I/O modules through a common DIN rail but you cannot substitute one adapter with the other.

Furthermore, FLEX 5000 series provide a wide variety of EtherNet adapters which can support up to 16 Safety or Standard I/O modules while the FLEX 1794 adapter series offers an I/O module capacity of 8. In addition, FLEX 5000 EtherNet/IP adapters are more intelligent and smarter due to their CIP Sync and PTP (Precision Time Protocol) network feature. Lastly, compared to FLEX 1794 adapters, FLEX 5000 adapters tend to be more secure as they support two different security enhancement measures: Implicit and Explicit Protected Modes.

HART I/O Modules Support

FLEX 1794 Series

In the 1794 FLEX series, HART analog modules can be used with EtherNet adapter Revision 4.2 or higher, ControlNet adapter Revision 5.1 or greater, and Profibus-DP adapter (but only the 1794-APBDV1 is compatible). Also, the FLEX 1794 HART® analog modules transmit HART data to the controller or asset management software for improved plant operations.

For example, the 1794-IE8H module accepts at most 8 analog inputs. Its inputs comprise selectable firmware digital filters and fixed hardware filters. The inputs are also non-isolated and their supply current is within two ranges: 4mA to 20mA or 0 to 20mA (which is the default range). Similarly, the 1794-OE8H output modules provide up to 8 analog outputs. These outputs are non-isolated and they provide current in two ranges: 0 to 20mA which is the default range and 4mA to 20mA.
Each of the 1794-HART I/O modules provides full functionality without jumpers or switches; local microprocessor intelligence to handle advanced HART features, lead breakage detection, remote transmitter alarm, multiple data ranges which can be programmed independently in channel groups and under range/over range alarms.

FLEX  5000 Series

The FLEX 5000 analog HART I/O modules are used to connect a Logix controller to a control process. The HART input modules in this series include 5094-IF8IHXT and 5094-IF8IH. They obtain raw signals from the process value transmitters, which they, in turn, convert to relevant measurement values (such as flow, pH, temperature, or Pressure) to be used by the Logix controllers. The FLEX 5000-HART output modules include 5094-OF8IH and 5094-OF8IHXT. These modules provide voltage or current signals that adjust the settings of field devices such as valves, according to the desired process behavior.

In addition, FLEX 5000 analog HART I/O modules use the Producer/Consumer network model to communicate with attached HART devices, controllers, and other I/O modules. This model is an intelligent communication model between the HART devices/ modules and other systems within. To configure the FLEX 5000 HART, I/O modules, and connected HART devices, Studio 5000 Logix Designer application version 32.02 or higher is used.

The key features of the FLEX 5000 HART I/O modules include 8-channel to channel isolated output and input modules, which make it possible to individually configure each channel as HART voltage or HART current. They also support HART V5, V6 and V7; current sourcing of isolated loop power; visible access to HART devices; information view of integrated devices and Readback functionality for outputs. Moreover, FLEX 5000 HART I/O modules support a new Logix Feature-Highly Integrated Hart (HIH). However, to be compatible with ControlLogix 5580 having the HIH feature, the HART I/O module must have a firmware revision 3.011 or later, to be able to support PlantPAx® HART and High Availability controller redundancy.


Both 1794 FLEX and 5000 FLEX Series support up to 8 analog input and output HART modules. The two series also enable connection to HART devices and transfer of HART data. However, the FLEX 5000 HART I/O modules are more advanced and smarter; allowing easy access, configuration, and management of highly integrated HART devices.

The simplified programming experience provided by Studio 5000 Logix Designer application; simplifies design, operational productivity, and maintenance of control systems. Overall, compared to the FLEX 1794 Analog-HART I/O modules, the FLEX 5000 highly-integrated HART I/O modules greatly improve the operational efficiency of machines through increased uptime.

Specialty I/O Modules

There are three specialty I/O modules within FLEX 1794 series, which include a very High-Speed counter module, Frequency modules, and Pulse Counter modules. While FLEX 5000 series only support one specialty I/O module which is the High-Speed Counter module. However, the latter provides several FLEX 5000 Safety I/O modules such as Safety Digital 16 Input/Output 24V DC, and Safety Relay 4 Isolated Output, in addition to the Standard Analog and Digital I/O modules also available within FLEX 1794 series.
Additionally, both FLEX 1794 and FLEX 5000 Series support configurable Thermocouple and RTD modules. The two FLEX series also have a simplified Removal and Insertion Under Power (RIUP) feature which allows you to easily replace modules and connect cables while the system is in operation. This online module significantly reduces downtime.

Which FLEX Series should I choose?

Only you as a control or design engineer know the specific requirements of your control system and the priorities for your application. Maybe you could be looking to maximize the uptime of your industrial process, or for faster communication rates within your network, or maybe you are looking for a highly flexible network (i.e., a common application protocol for ControlNet, DeviceNet, and EtherNet).

Or maybe you’re planning to enhance your system with intelligent and smart modules. Or you would prefer a broad portfolio of fail-safe I/O modules or highly-integrated HART I/O modules. Therefore, we have only provided you with different aspects of the 1794 FLEX I/O and FLEX 5000 Series, to consider as you determine the best fit for your control system. We hope that this comparison of  the 1794 FLEX I/O and the FLEX 5000 has been helpful in understanding your selection options.  For more information or to discuss which equipment might be best for your application, please visit our website here, or contact us at sales@pdfsupply.com or 1-919-535-3180. 

This entry was posted on September 21st, 2021 and is filed under Allen-Bradley, Automation, Hardware Comparison, Uncategorized. Both comments and pings are currently closed.

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