LEDs of the power supply in K-bus mode

After switching on, the power supply immediately checks the connected Bus Terminal configuration. Error-free start-up is signalled by the red "I/O ERR” LED being extinguished. If the “I/O ERR” LED blinks, an error in the area of the terminals is indicated. The error code can be determined from the frequency and number of blinks. This permits rapid rectification of the error.

Display	LED	Meaning
	Us 24 V	Power supply for the CPU module. The LED lights green if the power supply is correct.
	Up 24V	Power supply for terminal bus. The LED lights green if the power supply is correct.
	K-BUS RUN	K-bus diagnostics. The green LED lights up in order to indicate fault-free operation. "Fault-free" means that the communication with the fieldbus system is also running.
	K-BUS ERR	K-bus diagnostics. The red LED flashes to indicate an error. The red LED blinks with two different frequencies.

The I/O error LED blink code

Fast blinking	Start of the error code
First slow sequence	Error code
Second slow sequence	Error code argument

LEDs for K-bus diagnostics

Error code	Error code argument	Description	Remedy
Persistent, continuous flashing		EMC problems	Check power supply for overvoltage or undervoltage peaks. Implement EMC measures. If a K-Bus error is present, it can be localized by a restart of the power supply (by switching it off and then on again).
3 pulses	0	K-bus command error	No Bus Terminal inserted. One of the Bus Terminals is defective; halve the number of Bus Terminals attached and check whether the error is still present with the remaining Bus Terminals. Repeat until the defective Bus Terminal is located.
4 pulses	0	K-Bus data error, break behind the power supply	Check whether the Bus End Terminal 9010 is connected.
4 pulses	n	Break behind Bus Terminal n	Check whether the Bus Terminal n+1 is correctly connected; replace if necessary.
5 pulses	n	K-bus error in register communication with Bus Terminal n	Exchange the Bus Terminal on position n.
6 pulses	0	Error at initialization	Exchange Embedded-PC.
	1	Internal data error	Perform a hardware reset on the Embedded-PC (switch off and on again).
	8	Internal data error	Perform a hardware reset on the Embedded-PC (switch off and on again).
7 pulses	0	Process data lengths of the set and actual configurations do not correspond	Check configuration and terminals for consistency.

Error code argument

The number of pulses indicates the position of the last Bus Terminal before the fault. Passive Bus Terminals, such as a power feed terminal, are not included in the count.

In the case of some errors, rectification does not cause the power supply to leave the blink sequence. The power supply can only be restarted by switching its supply voltage off and on again.

The CX unit recognizes these terminals automatically on scanning, reads out the terminal types and automatically places them in the System Manager.

LEDs of the power supply in K-bus mode 2:

K-bus state

The K-bus status is saved in the state byte (see fig. K-bus interface “1”). If the value is 0 the K-bus is operating synchronously and without errors. If the value is <> ”0” there may be a fault, or it may only be an indication that the K-bus cycle is longer than the task, in which case it would no longer by synchronous with the task. The task time should be faster than 100 ms. We recommend a task time of less than 50 ms. The K-bus update time typically lies between one and five ms.

Bit 0 = K-Bus error
Bit 1 = terminal configuration has changed since the start
Bit 2 = process image lengths do not match
Bit 8 = no valid inputs (yet)
Bit 9 = K-bus input update not yet complete
Bit 10 = K-bus output update not yet complete
Bit 11 = watchdog
Bit 15 = acyclic K-bus function active (e.g. K-bus reset)

If there is a K-bus error, this can be reset via the IOF_DeviceReset function block (in the TcIoFunctions.lib).