Overview
The Allen-Bradley 1794-ASB /D is a Flex I/O Remote I/O (RIO) communication adapter module designed to bridge Flex I/O modules with RIO-capable controllers. This DIN rail-mounted adapter enables efficient distributed I/O configurations by connecting multiple Flex I/O modules to a central control system via the legacy RIO protocol. The /D series revision includes firmware updates for improved system stability and safe state recognition with Flex integral analog modules.
Key Features
- Supports communication with up to 8 FLEX I/O modules
- Configurable communication rates: 57.6 Kbps, 115.2 Kbps, and 230.4 Kbps
- DIN rail mounting with open-type enclosure requiring protective cabinet installation
- Built-in status indicators: Power LED, Adapter Active LED, Adapter Fault LED, and Local Fault LED
- Multiple addressing modes: standard, compact, complementary, standard-32, and complementary-32
- Block Transfer Read (BTR) and Block Transfer Write (BTW) instruction support for flexible data transfer
Technical Specifications
Power Supply
- Nominal Supply Voltage: 24 VDC
- Input Voltage Range: 19.2 to 31.2 volts DC
- Maximum Current Draw: 450 mA at 24V DC
- Power Dissipation: 4.6 Watts at 31.2 Volts DC
- Thermal Dissipation: 15.7 BTU/hour at 31.2 Volts DC
Communication
- Protocol: Legacy RIO protocol using Belden 9463 or equivalent cables
- I/O Modules Supported: Up to Eight (8) Flex I/O modules
- Baud Rates: 57.6 Kbps, 115.2 Kbps, and 230.4 Kbps
- Isolation Voltage: 500V AC
Physical
- Dimensions: Approximately 4 x 2 x 4 inches
- Weight: 6 ounces
- Mounting: DIN rail mounted with one Remote I/O communication port
- Operating Temperature: 0 to 55 °C (32 to 131 °F)
- Storage Temperature: -40 to 85 °C (-40 to 185 °F)
- Enclosure Rating: IP20, Open Type (requires protective cabinet)
Typical Applications
The 1794-ASB /D is deployed in legacy industrial automation systems requiring distributed I/O control across remote locations. Typical applications include:
- Steelworking, metal smelting, refrigeration, construction and textile machinery, and water treatment
- Machine tool controls with remote sensor and actuator networks
- Motion control and sequential relay control with analog process variable monitoring
- Multi-location I/O expansion where centralizing all I/O would be impractical
Compatibility & Replacements
Compatible With
- Allen-Bradley Legacy controllers: PLC2, PLC3, PLC5, and SLC500
- Modern Logix controller platforms as well as third-party devices and partner modules
- Flex I/O series modules (1794 family digital and analog I/O cards)
- Belden 9463 or equivalent Remote I/O communication cables
- Systems using Block Transfer instructions (BTR/BTW) for data exchange
Replaces / Drop-In Replacement For
This module’s alternate series include Series A, B, C, D, and Series E adapter modules. The /D revision is recommended as a direct replacement for earlier Series A, B, and C units, particularly when Flex integral analog module compatibility is required. Verify firmware revision and addressing mode compatibility with your existing system before substitution.
Works With
- Remote I/O (RIO) protocol networks and legacy scanning architectures
- Block Transfer (BTR/BTW) instruction-based programming models
- Standard, compact, complementary, standard-32, and complementary-32 addressing modes
- Flex I/O distributed I/O configurations supporting up to 8 local modules per adapter
- Industrial enclosures and DIN rail control panels (requires protective housing)
