Allen-Bradley 1771-DMC
Allen-Bradley 1771-DMC
Allen-Bradley 1771-DMC
Allen-Bradley 1771-DMC
Allen-Bradley 1771-DMC
Allen-Bradley 1771-DMC
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1771-DMC

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1771-DMC is a 1-slot control coprocessor with 256KB memory for complex math, production scheduling, protocol conversion, and high-speed search, operating in 1771 Universal I/O systems.
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Technical specifications for 1771-DMC

  • Manufacturer:
    Allen-Bradley
  • Part Number:
    1771-DMC
  • Product Family:
    PLC-5
  • Product Type:
    Control Coprocessor Module
  • Memory:
    256 Kbytes
  • Slot Requirement:
    1 slot (2 slots with serial expander)
  • Current Draw:
    2.50 Amps (main module)
  • Default TAG Table Size:
    0 (zero)
  • Station Address Range:
    0-77 octal
  • Weight:
    1.36 kg
  • Estimated shipping dimensions:
    28x16.5x5.1cm
  • Tariff Code:
    8517795000
  • Country of origin:
    USA
  • Place of shipment:
    Xiamen, Fujian, China
By purchasing this item, you agree to the Terms & Conditions, ApterPower is not an authorized distributor for listed manufacturers or tradenames and therefore the manufacturer's warranty does not apply. All our products come with ApterPower's 1-year warranty.

More Information

Overview Manuals Specifications Application Performance & Efficiency Application Scenarios

Features:

  • Executes complex math algorithms, custom application logic, and protocol conversion directly on the coprocessor without burdening the main PLC processor.
  • Supports TAG_DEFINE, TAG_READ, TAG_WRITE, and TAG_LOCK/UNLOCK functions for efficient shared memory access between the coprocessor and PLC.
  • Optional 1771-DXPS serial expander module adds communication ports; RAM SIMMs provide memory expansion; compatible with Ethernet versions (1771-DMC1, 1771-DMC4).
The 1771-DMC functions as an intelligent coprocessor that offloads computationally intensive tasks from the main PLC processor. Engineers can write custom C or BASIC programs to execute complex mathematical algorithms, such as PID calculations with non-standard equations, statistical process control functions, or application-specific formulas that would otherwise consume valuable PLC scan time.

The 1771-DMC implements a sophisticated TAG-based memory management system that simplifies data exchange between the coprocessor and the PLC. The TAG_DEFINE function creates named memory locations in the TAG table, allowing both processors to reference data by symbolic names rather than absolute addresses. The TAG_READ and TAG_WRITE functions provide controlled access to these tagged memory areas, with variations like TAG_READ_W and TAG_WRITE_W offering synchronized read/write operations that ensure data integrity.

The 1771-DMC is designed for scalability, allowing users to expand functionality as application requirements grow. The optional 1771-DXPS serial expander module adds additional serial communication ports, transforming the single-slot 1771-DMC into a two-slot configuration with enhanced connectivity for multiple field devices. For applications requiring more memory than the standard 256 Kbytes, RAM SIMMs can be installed in the coprocessor's SIMM sockets.

The 1771-DMC Allen-Bradley Control Coprocessor Module may still be available for purchase and support from Apter Power beyond End-Of-Life (EOL)by the manufacturer (OEM).

Allen-Bradley 1771-DMC Control Coprocessor Module Manuals, Datasheets,Drivers,Link Important Notice:Other accessories,manuals,cables,calibration data,software,etc.are not included with this equipment unless listed in the above stock item description.All prices are shown in USD.
Allen-Bradley 1771-DMC Control Coprocessor Module Specs

General

  • Manufacturer Allen-Bradley
  • Model 1771-DMC
  • Condition New Original ready stock
  • Product Family 1771-IL,1771-OWNA,1771-ACN15,1771-OBD
Important Notice:Other accessories,manuals,cables,calibration data,software,etc.are not included with this equipment unless listed in the above stock item description.All prices are shown in USD.
  • Complex Process Automation: Used in chemical, pharmaceutical, and water treatment industries to execute intricate mathematical algorithms, closed-loop PID formulations, and floating-point multi-variable calculations.
  • Legacy Factory Telemetry & Data Logging: Deployed in large-scale assembly lines, food and beverage plants, and automotive factories to serve as a local storage buffer for production metrics, alarms, and historical quality control logs.
  • Multi-Vendor Protocol Translation: Acted as a central communication gateway in hybrid industrial facilities where PLC-5 systems needed to interact with non-Rockwell automation equipment, such as weight scales, barcode scanners, and variable frequency drives (VFDs).
  • High-Speed Execution of Procedural Languages: Programmed in standard C or BASIC, the module ran complex formulas, text-string manipulations, and data sorting tasks infinitely faster and more efficiently than a standard PLC ladder logic routine could achieve.
  • Optimized Backplane Block Transfers: It communicated with the host PLC-5 processor using efficient Rockwell Block Transfer (BT) read/write commands across the 1771 backplane. This decoupled data crunching from the standard I/O scan loop, optimizing the overall scan time efficiency of the main control architecture.
  • Dedicated Dual-Port Memory Architecture: Equipped with onboard multi-kilobyte RAM (e.g., 256 KB), allowing it to hold large database look-up tables and communicate variables to the host processor smoothly without inducing backplane data-packet collisions.
  • A legacy PLC-5 system needed to pull real-time weight parameters from an external digital scale or command recipes to a non-Allen-Bradley serial controller.
  • Process calculations involving complex geometric curves, gas volume natural-gas correction equations, or high-order predictive algorithms that exceeded the math block capabilities of vintage PLC-5 ladder logic.
  • Multi-product manufacturing cells where rapid recipe changes were required, but the PLC-5 internal memory lacked the capacity to store hundreds of multi-step configuration arrays.
Description
The 1771-DMC is a 1-slot control coprocessor module in the 1771 Universal I/O System, featuring 256 Kbytes of memory. It can be used with or without a programmable controller, making it versatile for various automation applications. The 1771-DMC supports C and BASIC programming for complex math algorithms and application-specific calculations. 

The 1771-DMC requires 2.50 Amps of current draw from the backplane. When using the 1771-DMC, you must select an appropriate power supply based on total chassis current requirements including I/O modules, PLC/adapter modules, and optional serial expander modules (1771-DXPS). 

Configuration of the 1771-DMC is performed using the CC_CFG utility, which sets station address (0-77 octal), enables/disables PLC reset capability, and configures TAG table size. 

Applications for 1771-DMC include protocol conversion for interfacing PLCs with various field devices, historical data logging and tracking, and production scheduling. The 1771-DMC can be expanded with optional RAM SIMMs for additional memory. When using 1771-DMC, ensure proper TAG_LOCK and TAG_UNLOCK pairing to prevent system hang-ups. 
Revisions

Revision Part #

Also known as

1771-DMC Ser A
1771-DMC/A, Series A, Rev A
Alternative Names
1771DMC 177I-DMC 177IDMC I771-DMC I771DMC I77I-DMC I77IDMC
Technical notes
The 1771-DMC control coprocessor runs C/BASIC programs for complex automation tasks. Current draw: 2.50A. Use CC_CFG to set station address (0-77 octal), PLC reset, and TAG table size (default 0). Requires ESD-safe handling. Pair TAG_LOCK with TAG_UNLOCK to prevent system hang-ups. Optional 1771-DXPS expander adds serial ports. CSA/UL certified.
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FAQS

The following is a list of questions commonly asked by our customers. Please contact us if you have a question about our process that is not answered below.
What are the primary applications for 1771-DMC?
The 1771-DMC handles complex math algorithms using C/BASIC, production scheduling, historical data logging, high-speed search/compare of large files, and protocol conversion for interfacing PLCs with various field devices.
What is the current draw and power supply requirement for 1771-DMC?
The 1771-DMC draws 2.50 Amps from the backplane. Add this to I/O modules (step 1), PLC/adapter (step 2), plus Ethernet transceiver (3x current) and expander (1.50A) if used. Total determines power supply selection.
How do I configure the 1771-DMC default startup parameters?
Use the CC_CFG utility with syntax: cc_cfg -add=octal (station address 0-77), -rst=str (enable/disable PLC reset), -tag=num (TAG table size). Station address and reset take immediate effect; TAG size after next boot.
What is the default TAG table size for 1771-DMC?
The 1771-DMC default TAG-table size is zero, unlike 1771-DMC1 and 1771-DMC4 which default to 1024. If insufficient memory, zero remains default. Use TAG_DEFINE to create TAG entries in the table.

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