Overview
The Allen-Bradley 1771-SPI is a network master protocol interface module designed for Allen-Bradley PLC-5 systems. It facilitates bidirectional communication between PLC-5 processors and SPI-compatible peripheral devices including temperature controllers, material dryers, and other auxiliary equipment. This module acts as a protocol gateway, converting block-transfer commands into SPI network traffic.
Key Features
- RS-485 Multi-Drop Serial Interface: Electrically interfaces through RS-485 multi-drop serial port using Field Wiring Arm Connector
- High Device Count: Supports a maximum of 32 connected devices on the SPI link
- Flexible Baud Rate: Communication speed of 1200–19200 bits per second (with 1200 bps required and 9600 common)
- Standard 1771 Chassis Installation: Installs into any 1771 I/O chassis and is keyed to the chassis via connection between pins 12 and 14, 16 and 18
- Configurable Protocol Blocks: Processor writes command blocks with block-transfer write (BTW) instructions and reads status blocks with block-transfer read (BTR) instructions
- User-Defined Commands: Supports user-defined command allowing access to devices that may not have pre-defined I/O address but are electronically compatible with SPI protocol
Technical Specifications
- Backplane Current Draw: 1.3A at 5V DC
- Communication Protocol: SPI (Sensor Protocol Interface)
- Serial Interface: RS-485 multi-drop (asynchronous, half duplex)
- Baud Rate Range: 1200 to 19200 bits per second
- Device Support: Maximum of 32 connected devices on SPI link
- Logical Device Addresses: 128+ possible logical device addresses
- Operating Temperature: 0 to 60 degrees Celsius
- Storage Temperature: -40 to 85 degrees Celsius
- Operating Humidity: 5 to 95% relative humidity
- Storage Humidity: 5 to 85% relative humidity
- Series: Series C
- PLC Compatibility: PLC-5 systems
- Mounting: Single slot in 1771 I/O chassis with locking latch
Typical Applications
Use in conjunction with Allen-Bradley PLC controllers and any type of SPI-compatible plastic conversion machinery. Common applications include:
- Plastic injection molding systems with hot runner temperature control
- Material dryer integration (Conair Compu-Dry, similar devices)
- Industrial process control with distributed SPI devices
- Data acquisition from remote SPI-compatible sensors and controllers
- Custom manufacturing equipment requiring protocol gateway functionality
Compatibility & Replacements
The 1771-SPI Series C module is designed specifically for PLC-5 I/O chassis systems. It cannot be interchanged with a series A 1771-SPI module. The module communicates with the PLC processor via standard block-transfer instructions (BTW/BTR), making it compatible with all RSLogix 5 and Studio 5000 programming platforms that support PLC-5 legacy systems. This is a discontinued product as of December 2009, making it essential to verify module revision and firmware compatibility with your specific PLC-5 processor and application requirements before installation.
