Point I/O Compatibility Matrix

Compatibility Overview

The Allen-Bradley 1734 Point I/O platform is a modular, high-density distributed I/O system extensively deployed in industrial automation configurations. The architecture consists of a network communication adapter, terminal bases, and hot-swappable I/O modules that communicate across a proprietary internal backplane called the PointBus.

Inter-device compatibility within the 1734 system is determined by physical, electrical, and logical parameters. Physical compatibility relies on mechanical keying on the terminal bases (such as the 1734-TB and 1734-TBS). Electrical compatibility is governed by the 5V DC PointBus current limits and 24V DC field-side distribution. Logical compatibility is controlled by the module's electronic keying settings (Exact Match, Compatible Module, or Disabled Keying) configured inside the Rockwell Automation Studio 5000 Logix Designer environment.

Evaluating these parameters before installation prevents physical module damage, communication timeouts, and unintended I/O drops during runtime operations.

Supported Models

The table below details the compatibility mappings for the most widely used 1734 Point I/O modules, including their associated terminal bases, wiring configurations, and physical key positions.

All standard 1734 digital and analog modules are physically compatible with the standard 1734-TB (screw terminal block) and 1734-TBS (spring clamp terminal block). The terminal base must have its rotary orange keying dial set to the corresponding position listed in the table prior to inserting the electronic module to avoid damaging physical pins.

Unsupported Models

While the 1734 series offers high interoperability, legacy versions, specific third-party configurations, and outdated hardware layers are incompatible with modern 1734 systems:

• Legacy Adapters (1734-PDN, 1734-ADN Series A): These DeviceNet adapters lack the firmware capacity to map modern high-density models like the 1734-IB8 (8-channel input) or smart modules like the 1734-232ASC (Serial ASCII module) without restrictive mapping limits.
• Series A vs. Series B Module Hardware: Certain modules, such as early Series A editions of the 1734-IE2C, are structurally incompatible with older firmware revisions of the 1734-AENT adapter (specifically firmware versions below 2.001).
• Direct ControlNet Coupling with 1734-ACNR Series A: The 1734-ACNR has been deprecated and does not support modern Guard I/O modules (e.g., 1734-IB8S safety modules). Only active, updated platforms support safety-rated CIP Safety communications.
• Non-Isolated Module Grouping: You cannot mix AC modules (e.g., 1734-IA2 120V AC input) and low-voltage DC modules (e.g., 1734-OB4E) on the same physical power rail without inserting a 1734-FPD (Field Power Distributor) to physically isolate the voltage potentials on the field power bus.

Communication Options

Control processors coordinate communication with the 1734 Point I/O rack over various industrial networks using distinct physical adapters:

EtherNet/IP (1734-AENT / 1734-AENTR)

This represents the industry standard for Point I/O. The 1734-AENTR features an embedded two-port switch supporting Device Level Ring (DLR) topologies and linear architectures. Utilizing standard EtherNet/IP (CIP), it interfaces natively with ControlLogix and CompactLogix controllers. It supports both Unicast and Multicast options for cyclic I/O data connection management.

DeviceNet (1734-ADN)

Used for legacy architectures. Communications rely on standard DeviceNet trunklines and drop lines. The adapter maps the module memory up to 63 modules directly into a DeviceNet scanlist, which is then mapped via a scanner card to the host PLC.

Third-Party Protocols (PROFINET, Modbus TCP, EtherCAT)

While Rockwell does not natively manufacture native PROFINET or Modbus adapters for Point I/O, robust third-party communication options exist. Industry-certified network gateways from Encompass partners (such as HMS Anybus or ProSoft Technology) permit integration of standard 1734 I/O modules into PROFINET or Modbus TCP environments, converting standard CIP-based PointBus backplane commands into the host controller's native industrial protocol.

Integration Notes

Integrating Point I/O systematically requires strict adherence to power calculations and design configurations:

PointBus Power Sizing (5V DC)

The communication adapter provides a finite amount of 5V DC current to the backplane to power the inner circuitry of the attached I/O modules. For example, the 1734-AENT provides up to 1.0 A (1000 mA) of current.

$$\text{Total Current} = \sum_{i=1}^{n} I_{\text{module}, i} \le I_{\text{adapter}}$$

If the sum of module current draws exceeds the adapter limit, a 1734-EP24DC Expansion Power Supply must be inserted into the rack to refresh the PointBus voltage with an additional 1.0 A.

• 1734-IB8 Current Draw: 75 mA
• 1734-IE4C Current Draw: 75 mA
• 1734-OW4 Relay Current Draw: 80 mA

Field Power Sizing (24V DC / AC)

Separate from the logic bus, field power feeds physical sensors and actuators. The field power bus can carry up to 10 A. If your digital output modules collectively draw more than 10 A of field power, add a 1734-FPD Field Power Distributor to break the backplane power supply segment and safely inject a fresh external 10 A electrical feed.

Common Compatibility Issues

1. Code 16#0114 Electronic Keying Mismatch: This error occurs inside Studio 5000 Logix Designer when the configured major/minor revision of a module (such as a 1734-OB8E Series B Device) does not match the actual physical module inserted in the terminal base. Resolve this by modifying the Module Definition properties to Compatible Module rather than Exact Match if the physical revision is higher than the project file configuration.
2. PointBus Current Starvation: Symptoms include downstream modules randomly disconnecting, exhibiting a flashing green/red Module Status (MS) LED, or dropping communications entirely. Check your design load calculations and install a 1734-EP24DC power resource module immediately preceding the failed segment.
3. Terminal Base Keying Damage: Attempting to force a 1734 analog module into a terminal base keyed to position "1" (default digital) will snap the registration pins on the bottom of the module. Always verify that the orange mechanical key is dialed to the correct position (e.g., "3" for analog input) using a flatheads screwdriver before mounting the electronics.
4. AENT Connection Limit Reached: The 1734-AENT adapter has a connection limit of 20 CIP connections (TCP/IP). When using separate rack-optimization configurations or mapping too many modules as discrete, non-optimized connections, the PLC will fail to open connections to modules at the end of the chassis.

FAQ

Q: Can I mix digital and analog modules on the same 1734 Point I/O stack?

Yes. Digital and analog modules can reside on the same physical stack. Ensure that the total current draw does not exceed the 1.0 A logical PointBus threshold and that the field power routing aligns with the respective Module specifications.

Q: How do I choose between the 1734-TB and 1734-TBS terminal bases?

The 1734-TB and 1734-TBS are electrically identical. The difference is mechanical: the 1734-TB uses screw-terminal block connections, while the 1734-TBS utilizes spring-clamp connections, which provide superior vibration resistance in harsh environments.

Q: Is a 1734-EP24DC power supply required at the beginning of every Point I/O rack?

No. The network communications adapter (e.g., 1734-AENTR) incorporates a built-in power supply that energizes the initial sections of the rack. The 1734-EP24DC is only required when the accumulated backplane load of the modules exceeds the adapter's capacity or when segregating specific isolation zones.

Q: Can a 1734 module be hot-swapped while the system is powered?

Yes, Point I/O supports Removal and Insertion Under Power (RIUP). You can safely swap a faulty module with an identical hardware version while the remaining system is operational, as long as the surrounding environmental conditions are safe.