Allen-Bradley 1747-OCEBCBA SLC 500 Open Controller CPU Module

Allen-Bradley 1747-OCEBCBA SLC 500 Open Controller CPU Module - Image 2

Allen-Bradley 1747-OCEBCBA SLC 500 Open Controller CPU Module

The Allen-Bradley 1747-OCEBCBA is a specialized Open Controller CPU module within the SLC 500 platform, representing a distinct departure from conventional PLC processors. Rather than executing ladder logic through a proprietary real-time operating system, the Allen-Bradley 1747-OCEBCBA is an embedded PC-based controller that runs MS-DOS and supports custom control applications developed using the Open Controller API . This architecture allows engineers to implement control strategies using standard PC programming tools and languages, while still leveraging the rugged 1746 chassis and SLC 500 local I/O modules that form the backbone of the platform.

The catalog number 1747-OCEBCBA is decoded from Rockwell’s 1747-OCE ordering matrix, where the option letters define the installed hardware configuration. In this specific variant, the “B” option indicates 4 MB of system DRAM, the “C” option specifies a 10 MB FlashDrive, and the remaining letters identify MS-DOS as the operating system with no bundled application software . The Allen-Bradley 1747-OCEBCBA occupies the leftmost slot of a compatible 1746 chassis and provides local I/O scanning for up to 30 valid SLC expansion slots, enabling the controller to interface with standard digital and analog I/O modules through the backplane.

At the heart of the Allen-Bradley 1747-OCEBCBA is a 5×86 processor running at 100 MHz, paired with a dedicated local I/O scanner operating at 33 MHz . The module provides two serial ports: COM1 is fixed as RS-232, while COM2 is selectable between RS-232, RS-422, and RS-485, accommodating a range of peripheral devices including programming terminals, operator interfaces, and serial communication equipment. The Allen-Bradley 1747-OCEBCBA draws 2.25 A at 5 V DC from the backplane and requires a chassis fan for operation above 30°C ambient, with the full 0–60°C range available only when forced cooling is present .

Description

Technical Specifications

Parameter Name	Parameter Value
Product Model	1747-OCEBCBA
Manufacturer	Allen-Bradley (Rockwell Automation)
Product Type	SLC 500 Open Controller CPU Module
Product Family	SLC 500
Main CPU	5×86 at 100 MHz
Local I/O Scanner	188 at 33 MHz
System DRAM	4 MB
FlashDrive Storage	10 MB
Operating System	MS-DOS (loaded, no bundled application software)
Local I/O Capacity	Up to 30 valid SLC local-expansion slots
Serial Port 1	RS-232
Serial Port 2	RS-232, RS-422, or RS-485 (selectable)
Backplane Current	2.25 A at 5 V DC
Operating Temperature	0–60°C with chassis fan; 0–30°C without fan
Storage Temperature	-40–85°C
Relative Humidity	5–95%, noncondensing
Module Weight	Approximately 0.397 kg

Main Features and Advantages

PC-Based Open Control Architecture: The Allen-Bradley 1747-OCEBCBA distinguishes itself from every other SLC 500 processor by running MS-DOS as its operating system and exposing an Open Controller API that allows engineers to develop control applications using standard PC programming environments rather than proprietary PLC languages. This open architecture enables the implementation of custom algorithms, data logging routines, and communication protocols that would be difficult or impossible to express in ladder logic alone. For legacy systems with specialized control requirements, the 1747-OCEBCBA provides a path to maintain PC-based control without abandoning the existing 1746 I/O infrastructure.

Local I/O Scanning for SLC 500 Chassis: Despite its PC-based architecture, the Allen-Bradley 1747-OCEBCBA includes a dedicated local I/O scanner that supports up to 30 valid SLC expansion slots within the 1746 chassis . This allows the controller to interface with the full range of SLC 500 digital, analog, and specialty I/O modules, preserving existing field wiring and module investments. The scanner operates independently of the main CPU, ensuring that I/O updates continue even during application-level processing, which is critical for maintaining deterministic response in machine control applications.

Dual Configurable Serial Ports: The Allen-Bradley 1747-OCEBCBA provides two serial communication ports with flexible configuration options. COM1 is fixed as RS-232 for connection to programming terminals or simple peripherals, while COM2 supports RS-232, RS-422, and RS-485, enabling longer-distance communication and multi-drop network topologies . This serial flexibility allows the controller to integrate with legacy operator interfaces, barcode scanners, weigh scales, and other serial devices commonly found in installed SLC 500 systems.

Matched Memory and Storage Configuration: The 1747-OCEBCBA configuration includes 4 MB of DRAM and a 10 MB FlashDrive, providing sufficient storage for the MS-DOS operating system, custom control applications, and data logging requirements. The FlashDrive serves as the non-volatile storage medium for the application image and DOS startup files, ensuring that the controller can boot and resume operation after power restoration without requiring manual intervention . When replacing a 1747-OCEBCBA, preserving the complete FlashDrive image is essential, as the replacement unit does not ship with application software or a preconfigured system image.