Allen-Bradley 1784-KTXD Replacement for 1784 Series

Product Overview

Allen-Bradley 1784-KTXD Replacement/Upgrade Solution for 1784 Series: Smooth Migration from Legacy ISA-Bus Communication Platforms

The Allen-Bradley 1784-KTXD is an ISA-bus PC communication card designed for dual-port DH+ and ControlNet connectivity, enabling host PCs running RSLinx Classic or legacy programming software to communicate directly with PLC-5, SLC 500, and MicroLogix controller families over the Data Highway Plus (DH+) network. As ISA-slot motherboards reach end-of-life and industrial PCs are refreshed, the 1784-KTXD has become one of the most actively sought legacy communication cards for both direct replacement and controlled migration projects.

Whether your facility is maintaining an aging DH+ backbone, replacing a failed card in a critical programming workstation, or planning a phased migration away from ISA-based communication infrastructure, this 1784-KTXD unit ships tested, inspected, and backed by a 12-month warranty — ready to restore your communication link with minimal downtime.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful 1784-KTXD replacement or migration rarely involves a single component. In most field scenarios, the communication card is one node in a broader DH+ or ControlNet architecture that includes multiple interdependent components. During the upgrade or replacement process, engineers commonly address the following associated hardware in the same maintenance window.

On the controller side, the DH+ network typically terminates at a PLC-5/20, PLC-5/40, or PLC-5/80 processor installed in a 1771 I/O chassis. These processors communicate over DH+ via their built-in port, and the 1784-KTXD serves as the PC-side bridge. If the PLC-5 processor itself is being replaced or upgraded as part of the same project, the 1785-L40B or 1785-L80B processor modules are common targets. For facilities transitioning to ControlLogix, the 1756-L61 or 1756-L63 ControlLogix processor with a 1756-DHRIO communication module provides a structured migration path that preserves the existing DH+ wiring infrastructure while introducing modern Ethernet/IP capabilities.

On the network infrastructure side, DH+ segments rely on proper termination and cabling. The 1770-CD DH+ cable and associated 1770-XD termination resistors are frequently inspected and replaced during the same service visit. Faulty termination is a leading cause of intermittent DH+ communication errors that are often misdiagnosed as card failures.

For facilities running ControlNet alongside DH+, the second port on the 1784-KTXD connects to a ControlNet segment. Associated hardware in this environment includes the 1786-RPA/B ControlNet repeater and 1786-TPYR ControlNet tap, both of which are commonly stocked as spares when a communication card replacement is being planned.

In SLC 500 environments, the DH+ port is typically provided by a 1747-KE DH+ communication module installed in the SLC 500 chassis, or by the onboard DH+ port on a 1747-L551 or 1747-L553 SLC 5/05 processor. The 1784-KTXD connects the programming PC to these controllers without requiring any changes to the SLC rack wiring or I/O configuration.

For MicroLogix installations, the MicroLogix 1000 (1761-L16BWA) and MicroLogix 1500 (1764-LSP) communicate over DH+ via the 1784-KTXD using RSLinx Classic drivers. No additional communication modules are required in the controller, making the card replacement a straightforward swap at the PC end.

When the replacement project involves upgrading the programming workstation itself — moving from an ISA-slot industrial PC to a modern PCI or PCIe platform — the 1784-PKTX (PCI DH+/ControlNet card) or the 1784-PCMK (PCMCIA card for laptops) are the natural successors, maintaining full RSLinx Classic driver compatibility while eliminating the ISA bus dependency.

Retrofit Guidance FAQ

Q: Can I install the 1784-KTXD without changing my RSLinx Classic driver configuration?
A: Yes. If you are replacing a failed 1784-KTXD with an identical unit, RSLinx Classic will recognize the card using the existing driver configuration. You may need to re-assign the IRQ and I/O address in the card’s jumper settings to match your previous configuration, but no driver reinstallation is required in most cases.

Q: Is the 1784-KTXD compatible with Windows 10 or Windows 11 programming workstations?
A: The 1784-KTXD requires ISA bus hardware and 16-bit ISA drivers. Modern operating systems (Windows 10/11) do not natively support ISA bus devices. This card is intended for use with legacy industrial PCs running Windows XP, Windows 7 (32-bit), or dedicated embedded OS environments that retain ISA slot support. For modern PCs, the 1784-PKTX (PCI) is the recommended migration path.

Q: Will replacing the 1784-KTXD require changes to the PLC program or I/O configuration?
A: No. The 1784-KTXD is a PC-side communication interface only. It does not affect the PLC program, I/O table, or controller configuration. The PLC-5, SLC 500, or MicroLogix program continues to run unchanged. Only the PC-side RSLinx driver configuration may require minor adjustment.

Q: What DH+ baud rate should I configure on the replacement card?
A: Match the baud rate to your existing DH+ network. Common settings are 57.6 kbps (default for most PLC-5 networks) and 115.2 kbps. The baud rate is set via jumpers on the 1784-KTXD card. Mismatched baud rates are a common cause of communication failure after card replacement.

Q: Can the 1784-KTXD be used for ControlNet programming simultaneously with DH+?
A: Yes. The 1784-KTXD provides two independent ports — one for DH+ and one for ControlNet. Both can be active simultaneously under RSLinx Classic, allowing the programming PC to communicate with both DH+ and ControlNet devices without switching cables or configurations.

Q: What physical space does the card require?
A: The 1784-KTXD is a half-length ISA card. It requires one available 16-bit ISA slot in the host PC. The card does not require external power beyond the ISA bus supply. Ensure adequate clearance for the dual-port connector bracket at the rear of the PC chassis.

Warranty Assurance

Every 1784-KTXD unit shipped from TOPNLMS is subject to a pre-shipment functional inspection covering power-on self-test, port integrity verification, and communication loopback testing where applicable. Units are shipped in anti-static packaging with appropriate cushioning for international freight.

12-Month Warranty Coverage: All units carry a 12-month warranty from the date of shipment, covering defects in materials and workmanship under normal operating conditions. Warranty claims are processed with priority response — typically within 24–48 business hours of receipt of the defective unit.

Replacement Support: In the event of a warranty claim, TOPNLMS will ship a replacement unit upon confirmation of the defect. For critical production environments, advance replacement arrangements can be discussed at the time of order to minimize downtime exposure.

Stock Availability: Units are stocked in Xiamen, China, with standard international shipping via DHL, FedEx, or UPS Express. Typical transit times to North America and Europe are 3–7 business days. Expedited shipping options are available upon request.

Procurement Assurance: TOPNLMS specializes in legacy and hard-to-source industrial automation components. Each unit is sourced through verified supply channels and undergoes condition assessment before listing. Certificates of conformance and shipping documentation are provided with every order.