Diagnostics On The Slave Side - Beckhoff CX8110 Manual

Configuration
6.6.3

Diagnostics on the slave side

The status of the EtherCAT communication is monitored using the state variable on the CX8110 side. Use
the variables DcToTcTimeOffset, DcTimeDiff and Dc State to monitor the status of the distributed clocks
(DC). These variables are created automatically when you enable distributed clocks (DC).
State (WORD):
The state variable is used to monitor the status of the EtherCAT communication. The communication is
active when the state is 0x___8.
0x___1 = Slave is in 'INIT' state
0x___2 = Slave is in 'PREOP' state
0x___4 = Slave is in 'SAFEOP' state
0x___8 = Slave is in 'OP' state
Other bits are reserved and do not have to be checked.
NetId (ARRAY[6] OF BYTE):
the NetId is the ADS number for the EtherCAT slave.
DcToTcTimeOffset (LINT):
indicates the time difference between master and slave clock. The slave clock is the clock of the CX8110
and can be read with _TaskInfo[1].
Code:
VAR
PlcTaskSystemInfo :PlcTaskSystemInfo;
END_VAR
PlcTaskSystemInfo:=_TaskInfo[1]; //Task Info wird and die PlcTaskSystemInfo Struktur übergeben
GVL.DcTimeFromCX8110:=PlcTaskSystemInfo.DcTaskTime; //Die DC Zeit wird ermittelt und einer Globalen
Variable zugewiesen
DcTimeDiff (DINT)
The DcTimeDiff variable indicates the accuracy of the distributed clocks (DC). The unit of measurement is
ns. Depending on the PLC program, the CX8110 takes approx. 1 to 2 seconds to adjust. In exceptional
cases, the CX8110 may take longer.
The shorter the sync task, the faster and better the CX8110 is tuned. The disadvantage is a higher CPU
load. So the rule is: as fast as possible, but without overloading the CPU. Make sure the CPU load is below
60%.
You can determine when the CX8110 is synchronized by reading the value of the DcTimeDiff variable. A
control configuration can be regarded as optimal with a task time of 1 ms and a DcTimeDiff of less than 10
ns. A DcTimeDiff of less than 100 ns is regarded as adequate.
1 ms = 1,000 µs = 1,000,000 ns
These demands are quite high. Depending on the application, a lower accuracy may be acceptable. You
should always determine whether the control quality is adequate for your application.
DcState (UINT):
With the CX8110 the value is always 0x___2.
0x___1 = TwinCAT Time Controlled by EtherCAT Slave Dc time
0x___2 = TwinCAT Time Controlled by CCat time
CX8110 Version: 1.4 47