GE GFK-2193A Commreq Programming Requirements and Recommendations, Error Detection and Handling

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COMMREQ Programming Requirements and Recommendations

COMMREQ instructions should be enabled by a contact from a transition coil.

If using more than one COMMREQ in a ladder program, verify that a previous COMMREQ executed successfully before executing another one. This can be done by checking the Status Word and the FT (Fault) output.

The FT output is held False if the Enable Input is not active. This means that if the COMMREQ is enabled by a transitional (one-shot) contact and a fault occurs, the FT output is High for only one PLC scan. To capture the fact that a fault occurred, you can program the fault output as a Set coil, which would not be automatically reset at the end of a scan. Additional logic would then be needed to reset the fault output coil after the fault is acknowledged and before the next execution of the COMMREQ.

Programming a device, such as a Set Coil, on the FT output of the COMMREQ is optional; this output may be left open if desired.

It is necessary to initialize the data in the Command Block before executing the COMMREQ instruction. Since the normal PLC sweep order is from top to bottom, initializing the Command Block in an earlier rung (or rungs) than the rung that contains the COMMREQ will satisfy this requirement.

Error Detection and Handling

As shown in “COMMREQ Status Word”, a value of 1 is returned to the Status Word if communications proceed normally, but if any error condition is detected, a value greater than 1 is returned. If you require error detection in your ladder program, you can use a Greater Than (GT) compare instruction to determine if the value in the Status Word is negative (less than zero). If an error occurs, the GT instruction’s output (Q) will go high. A coil driven by the output can be used to enable fault handling or error reporting logic.

The FT output of the COMMREQ, described on page 4-4,goes high for certain faults and can be used for fault detection also. Additionally, the first Status Word can be monitored by error message logic for display on an Operator Interface device, in which case, Status Word codes would correspond to appropriate error messages that would display on the operator screen.

To dynamically check the Status Word, write a non-significant positive number (0 or 99 are typically used) into the Status Word each time before its associated COMMREQ is executed. If the instruction executes successfully, the CPU will write the number 1 there. This method lets you know that if the number 1 is present, the last COMMREQ executed successfully, and that the 1 was not just left over from a previous execution.

When multiple COMMREQs are used, it is recommended that each be verified for successful communications before the next is enabled. Monitoring the Status Word is one way to accomplish this.

Corrective Actions for COMMREQ Errors

The type of corrective action to take depends upon the application. If an error occurs during the startup or debugging stage of ladder development, you should verify the COMMREQ parameters. The same is true if an error occurs right after a program is modified. But, if an error occurs in a proven application that has been running successfully, the problem is more likely to be hardware-related. The PLC fault tables should be checked for possible additional information when troubleshooting Status Word errors.

GFK-2193A

Chapter 4 Status and Diagnostics

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Contents GE Fanuc Automation Programmable Control ProductsAs Used in this Publication CimstarContents Contents Profibus Information Overview and SpecificationsRelated Publications IC693PBS201 Slave Module Specifications KeyProfibus Network Overview Profibus BasicsBus Communication Network Topology Amount of Data Transmission Duration FrequencyNetwork Connectors Pin No Signal DesignationReviewing System Power Requirements InstallationInstalling the Profibus Module in the PLC Rack Network Segment Length Connecting the Slave to the Profibus NetworkBaud Rate Line a Line B Glass Fiber Distance Max 1 Profibus Cable Types Network TerminationNetwork Baud Rate Removing the Module from the RackConfiguration Adding a Profibus Slave Module to the Hardware ConfigurationConfiguring a Profibus Slave Module Settings TabInput Data Area Tab Profibus Slave Module’s Input Data Area ParametersPower Consumption Tab Output Data Area TabProfibus Slave Module LED Indicators Status and DiagnosticsColor Indication Status/Firmware ID Array Network Parameter ErrorsWord 1 Slave Status Word Sysid Examples Communication RequestsCommreq Ladder Instruction Slot Word ValueOperation of the Communications Request PLCCorrective Actions for Commreq Errors Error Detection and HandlingCommreq Programming Requirements and Recommendations Commreq Status Word Value DescriptionGet Slave Status Commreq Get Slave Status Command Block Basic ExampleProfibus Slave Module Commreq Reference Memory TypesGet Slave Status Reply Data Format Bit Meaning ValueNetwork Parameter Errors Read Module Header Read Module Header Command Block Basic ExampleValue Type Dec Hex Description Read Module Header Reply Data Format for Slave Clear Counters Clear Counters Command Block Basic ExampleClear Counters Reply Data Format Index

GFK-2193A specifications

The GE GFK-2193A is a versatile and powerful programmable logic controller (PLC) designed for industrial automation applications. With its robust construction and advanced features, the GFK-2193A is ideal for industries that demand high reliability and flexibility in their control systems.

One of the standout features of the GE GFK-2193A is its processing power. It is equipped with a high-speed CPU that can handle complex tasks and large volumes of data efficiently. This allows for real-time decision-making and control, making it suitable for critical applications where timing and accuracy are paramount. The processing speed is complemented by a multitasking capability, enabling the controller to manage multiple processes simultaneously without a drop in performance.

The GFK-2193A also boasts an extensive range of input and output options. It supports a variety of digital and analog I/O modules, allowing for seamless integration with different sensors, actuators, and devices. This flexibility makes it easy to customize the system according to specific operational needs, whether it's for small-scale automation or extensive industrial setups.

In terms of communication capabilities, the GE GFK-2193A includes support for multiple industrial communication protocols. This includes Ethernet, Modbus, and Profibus, among others, ensuring compatibility with a wide array of devices and systems. The controller's ability to communicate effectively helps facilitate data exchange, enabling better coordination and monitoring across different components of an automation system.

Another significant feature of the GE GFK-2193A is its programming environment. It utilizes the popular Ladder Logic programming language, which is widely regarded for its ease of use and efficiency. Additionally, the controller supports other programming languages, like Function Block Diagram and Structured Text, providing users with the flexibility to choose the most suitable method for their application.

The durability of the GFK-2193A is another remarkable characteristic. Designed to withstand harsh industrial environments, it features robust housing and components, making it resistant to dust, moisture, and temperature fluctuations. This ensures long-lasting performance with minimal maintenance needs, enhancing overall operational efficiency.

In summary, the GE GFK-2193A is a comprehensive solution for industrial automation that combines processing power, flexibility in I/O configurations, advanced communication capabilities, and a user-friendly programming environment. Its robust construction ensures reliability even in challenging conditions, making it a trusted choice for industries looking to enhance their automation processes.
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