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.
| 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)