RTA's Blog
How to Move ASCII Data to an Allen-Bradley PLC Without Custom Code
Feb
The most efficient way to move ASCII data to a ControlLogix or CompactLogix PLC is by using an EtherNet/IP to ASCII Gateway. Unlike legacy methods that require writing custom “Socket Messaging” or complex ladder logic, a dedicated gateway maps ASCII strings directly into the PLC’s Tag database as standard Controller Tags.
Why Manipulating ASCII data in a PLC is an Engineer’s Nightmare?
Integrating ASCII barcode, printer, RFID or scale data into any programmable controller requires the engineer to handle handshaking, delimiters and string parsing manually within the PLC logic. That’s like riding a bicycle with two flat tires. You can certainly get where you are going, but it will take you a long time and the ride will be extremely rough.
PLCs aren’t built to manipulate data like this. They are built to process relay logic and scan I/O. When you use them to do data manipulation, the code will be brittle and difficult to maintain. Compare the complexity of using PLC logic to dedicated ASCII gateways.
| Metric | PLC Custom Socket Messaging | Gateway |
|---|---|---|
| Setup Time | 4-12 Hours | < 10 Minutes |
| Logic Complexity | High (Complex Rungs) | Zero (Tag-based) |
| Solution Support | Hard (Code-dependent) | Easy (Web UI) |
| Hardware Cost | Low | Moderate |
| Total Cost of Ownership | High (Engineering Hours) | Very Low |
What are the Limitations of Including an ASCII Gateway in a Control System?
ASCII gateways require support from the maintenance team, who must be familiar with the configuration and they are a secondary point of failure in the system.
RTA ASCII Gateways: A Better Choice for Moving ASCII Data Into Allen-Bradely PLCs
RTA ASCII gateways offers numerous advantages over legacy methods and competing solutions:
- Physical Connectivity – Support for ASCII devices using RS232, RS422or RS485, including hardware and software flow control
- Message Parsing – Automatic removal of leading and trailing strings that define the start and end of ASCII messages
- Data Manipulations – Conversion of ASCII numbers into numeric, float, double and other data types that PLCs can easily use
- Diagnostics – Integrated diagnostic counters and logs that assist you in diagnosing communication errors
- Easy and Flexible Logic Interface – Options ranging from simple In-block and Out-block transfers to making ASCII devices act like and EtherNet/IP Adapter
How Do I Choose the Best RTA ASCII Gateway for my Application?
When deciding which ASCII gateway you need, follow a few simple rules:
- For transferring uncomplicated barcode data, use a standard ASCII gateway that moves string data into a PLC string tag like the 435NBX.
- For transferring a few pieces of numeric data in a string (“Tare Weight: 123.4, Gross Weight: 150.x”), use a more advanced ASCII gateway, like the 460ETCA, that can extract and convert ASCII to other data types.
- For transferring ASCII data over an EtherNet/IP, Modbus TCP or PROFINET connection, use the 460TCPA protocol ASCII gateway.
FAQs
No, an AOI is usually not required unless the ASCII data is exceptionally complex. Most of the time, the ASCII data is simply transferred into the equivalent of a string tag in the PLC.
Yes, some gateways have the ability to extract a series of ASCII characters like “123.4” and convert that to an integer (123) or a float (123.400). That data can be written directly to the tag or transferred over PROFINET or EtherNet/IP if the gateway supports a more advanced communication protocol.
Summary
ASCII gateways are a valuable tool in a Control Engineer’s toolbox. RTA provides some of the most flexible ASCII gateways on the market to quickly you’re your valuable ASCII data to Allen-Bradley ControlLogix and CompactLogix PLCs.
