Cyclic process data PDO
Two terms are introduced for the EL6695, for the purpose of differentiation
- “Symmetric PDO mapping”: the same process data, in terms of size and sequence, are created on both sides
- “Selective PDO mapping”: one side loads a maximum volume of process data into the EL6695, from which the master on the other side selects a subset and requests it as cyclic process data.
Key data (as of 2015-06, FW04, TwinCAT 3.1 b4018.4):
● Max. 255 variables per direction (max. 255 entries in 0x1A08:nn and 0x1608:nn managed through TwinCAT, if PDOs are created manually).
● Maximum total PDO size: MTU (~1500 bytes), i.e. one Ethernet frame for direction, corresponding to approx. 1408 bytes user data. Larger quantity on request, requires adaptation in TwinCAT.
● Minimum PDO size is one byte, bit-PDOs are not permitted.
Changes in the configuration do not take effect until the respective EL6695 side is restarted.
For each 6000-type object, the system searches for a corresponding 7000-type object on the other side – e.g. 6001:05 → 7001:05. The size of the object on the other side (7000-type) must be equal to or greater than the 6000-type object. In so far it is also possible to copy a subset 7000 → 6000, cf. “selective PDO mapping”.