Cyclic memory access

Data traffic with cyclic process data

The user can create one set of process data with an arbitrary structure, max. 1280 bytes. This data set can be written cyclically in its entirety to the box or read by it. Individual access to the constituent parts of this data set is not possible (keyword: addressing). Control is performed by the task by means of a handshake via Control/Status Word, so that several task cycles may be necessary for saving or reading back, depending on the extent of the data and the cycle time.

When the EP6080-0000 is switched on, the regularly stored data from the last operating session are immediately available for reading via the inputs.

Commissioning: the cyclic process image must be created identically at inputs and outputs, max. 1280 bytes. Creation by right-clicking on "IO Inputs" or "IO Outputs".

Cyclic memory access 1: — Manual creation of the cyclic process data

If the input and output are created in different sizes, the box start fails: "PREOP to SAFEOP failed".
If more than 1280 bytes are created, the box start fails with "Invalid SM In/Out Cfg".

The data to be written from the task to the EP6080-0000 is output via the PDO "IO Outputs".
The last valid data received from the EP6080-0000 arrives at the task as read data via the PDO "IO Inputs" without further action.

	Restriction up to and including TwinCAT 2.10 The structure of the Input/Output data is subject to the following restriction up to TwinCAT 2.10 build 1330: all defined variables must be composed of n*bytes; individual bits or such types of composed structures are not permissible. If such data is defined, the EP6080-0000 attains the OP state, but reports an error due to Working Counter = 1. Examples of permissible configurations: Example of an invalid configuration:

Cyclic operation with handshake, recommended operating sequence:

1. Output of the input data to the box, set "Control" to the value 1.

If the box has successfully transferred the data, "Status" = 1 is returned.

2. Set "Control" to the value 0.

3. Wait until "Status" = 0 is returned.

The box is ready for a new write access.

Cyclic memory access 5: — Cyclic operation with handshake

Typical example of a measurement on the EL6080 for a cyclic write process according to the sequence specified above: (Beckhoff reserves the right to make unannounced changes)

20 bytes: 200 µs
1250 bytes: 2.5 ms

	Process data image and frame length In the case of short cycle times, an extensive process image for the EP6080-0000 can result in an Ethernet frame that is longer than the cycle time. Therefore, in order to use the entire 1280 bytes of the cyclic process image, the cycle time must be at least 200 µs.