SendClockFactor¶
The SendClockFactor multiplied with a basic time of 31.25 µs defines the cyclic basic clock rate of the whole PROFINET system, i.e. the smallest cycle time for the exchange of process data. The typical value for the SendClockFactor is 32, that means the basic bus cycle is 1 ms. For 100 MBit/s it is recommended that the SendClockFactor is between 5 an 128.
| SendClockFactor | PROFINET basic cycle time | Annotation |
|---|---|---|
| 5 | 156 µs | Fastest theoretical value for the basic cycle time at 100 MBit/s |
| 32 | 1 ms | Fastest basic cycle time for the PROFINET IO controllers |
| 128 | 4 ms | Slowest theoretical value for the basic cycle time at 100 MBit/s |
Note
The possible values for SendClockFactor and ReductionRatio (the product of both is the cycle time) of a CI506-PNIO device are dependent on the connected CANOPEN Slaves (number of PDOs. The dependency is shown in the following table.
For a CI506-PNIO for example:
| PROFINET Cycle Time | Maximum number of CANOPEN PDOs *) |
|---|---|
| 1 ms | 8 |
| 2 ms | 32 |
| 4 ms | 128 |
| 16 ms | 244 |
*) Remarks:
- 50 % RPDO, 50 % TPDO
- 8 byte process data for each PDO
- CANOPEN cycle time min. 4 ms or about 80 % CAN bus load (e.g. 20 ms for 128 PDOs)