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How does the 'SYSSTATE' block work in Concept?

Goals and Symptoms

The purpose of this resolution is to explain how the IEC function block 'SYSSTATE' works in Concept.

Facts and Changes

This resolution applies to all versions of Concept.

Causes and Fixes

The SYSSTATE function block has three outputs namely COLD, WARM and ERROR.
Listed below are the different scenario under which the outputs of the SYSSTATE block will turn ON.

1. When the PLC goes through a power cycle (also known as cold start), the WARM output alone will turn ON.
2. When the PLC is stopped and re-started from the On-Line Control Panel (no program download), the WARM output alone will turn ON.
2. When the Controller is stopped and re-started after a program has been downloaded, the COLD and WARM outputs will both turn ON.
3. There is no unique condition for the COLD output alone to turn ON.
4. When the fault messages in the error buffer have not yet been read, the ERROR output will turn ON.

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