Acyclic data transmission of parameter bits

An acyclic data exchange to change parameter bits of a device must be explicitly initiated by the user. A 4-bit data range within the cyclic basic cycle is provided for acyclic data exchange. This allows a one-time acyclic data exchange to be performed with exactly one device in a basic cycle. An acyclic data exchange of parameter bits with 31 devices will therefore take 31 cycles.

The time span of an acyclic data exchange results from the following:

  • Duration of the basic cycle (maximum 5 ms)
  • Duration that is required to initiate the acyclic service within the PLC.

If the parameter bits are changed on multiple devices, the change will take several times longer.

Device type

Device profile

Data width of payload data

Minimum bit rate with maximum
possible number of devicesIt is assumed that the acyclic parameters are written for all devices.

Bit/s

Binary devices

S-7.F

4 PO

25

4 PI

25

A/B device
or
double device
(A device)

S-7.A.7 (CTT3)

3 PO

10

4 PI

13

S-7.A.A (CTT3)

3 PO

10

4 PI

13

The following figure shows the maximum expected transmission time for the acyclic data exchange of parameter bits:

t

Transmission time, [t] = ms

N

Number of devices with which an acyclic data exchange of parameter bits takes place.

[1]

Maximum transmission time with a cycle time of 5 ms and 31 binary devices or 31 A-addressed A/B devices

[2]

Maximum transmission time with a maximum cycle time of 10 ms and 62 devices