PLC-5 System

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Communication Modules

PLC BASIC Module



The PLC BASIC Module (1771-DB) occupies one slot in the 1771 I/O chassis and runs user-written BASIC and C programs. These programs are independent of the PLC processor and provide an easy, fast interface between a PLC processor, 1771 backplane and RS-232, -422, or -485 devices. The BASIC module can also communicate with a remote SLC processor or remote device on the DH-485 network through a DH-485 port.

The PLC BASIC Module allows for:

• Creation of an interface between foreign device and the PLC processor.
  
• Manipulation and analysis of data gathered from the PLC and SLC processors.
  
• Communication with devices requiring remote communication, such as computers, modems, printers, and other third party devices.
  
• Calculation of complex math or application-specific algorithms, which helps conserve valuable PLC processor memory.
  
• Generation of unattended reports.
  

Configure the two ports for RS-232, -422, or -485 communication. The third port is for DH-485 communication or programming. The module provides up to 32K bytes of battery-backed RAM, and 24K bytes are available for user programs. With the BASIC Module, up to 32K bytes of EEPROM (optional) is available. The module also contains a time-of-day clock/calendar with 10 ms resolution.

To facilitate program development, order BASIC Development Software (1771-PBASE). This package runs on an IBM-compatible computer and lets users create, edit, translate, debug, upload, and download programs to the BASIC Module. Although the primary programming language is BASIC, both a C compiler and a C Toolkit from one of the Encompass Program partners is available in the C programming language.

Benefits

• Block-transfer capability minimizes user programming by allowing the module to transfer entire files of data back and forth between the module’s memory and the processor’s data table.
  
• The module supports BASIC commands and statements, and an additional 128 calls specific to the BASIC Module.
  
• The module has two ports configurable for RS-232, -422, or -485 communication. The third port is for DH-485 communication or programming.
  

Typical Applications

The BASIC Module interfaces to:

• Any device that needs an RS-232, -422, or -485 interface to a 1771 backplane
  
• Bar-code readers
  
• Scales
  
• Displays
  
• Modems
  
• Printers
  
• Robots
  
• Weld controls (for protocol conversion)
  

Specifications

Cat. No.	1771-DB
Isolation	500V DC from port-to-port and port-to-backplane
Communication rates	300, 600, 1200, 2400, 4800, 9600 or 19.2 kbit/s
Communication rates versus distance in feet	RS-232-C: 300…19.2 Kbps: 15 m (50 ft)
	RS-422: 300…19.2 Kbps: 1230 m (4,000 ft)
	RS-485: 300…19.2 Kbps: 1230 m (4,000 ft)
Time-of-day clock accuracy	Resolution 1s; ±1 minuten/month @ 25 °C +0, -6 minute @ 60 °C
Real-time clock	Resolution 10 ms; better than 0.1% accuracy
Backplane current load	0.75 A - with a DH-485 Interface/Converter (1747-PIC) connected to the DH-485 port
	0.65 A - without a device connected to the DH-485 port
Indicators	8 defined indicators 2 user-defined indicators
Certifications⋆	UL, CSA Class I Div 2 Hazardous, CE
⋆ When product is marked. See the Product Certification link at http://www.ab.com for Declarations of Conformity, Certificates, and other certification details.