Principle of operation


The KL6401 sends single SNVT variables. This means that an SNVT variable sent to the KL6401 is sent to the LON network individually. Only when this has successfully been sent can the next SNVT variable be transferred to the KL6401.


The KL6401 has 2 buffers, the telegram buffer and the index buffer.

The input variables of a LON telegram that has been received are placed in the telegram buffer. The index number of the incoming telegram is also entered into the index buffer.

The TwinCAT LON function block evaluates the index buffer, transfers input variables that have been received to the application program, and removes them from the index buffer. If the function block does not read the data out of the telegram buffer quickly enough, it can save up to 62 entries (i.e. the maximum number of SNVT variables).

If a telegram that has already been received (which the function block has not yet transferred to the application program, and which therefore still has an entry in the index buffer) is received from the KL6401 again, then a new entry is not made in the index buffer, but the input variables in the telegram buffer are updated.