Which products are affected?
E94AYCER FW 1.10 communication module
Functional description
The Ethernet 2-port switch on the communication module enables a line topology to be set up.
Applications
A line topology is typically used to achieve the shortest cable lengths - no extra switches are needed for the cabling.
Note:
The integrated switch of the 2-port Profinet I/O communication module results in delays to the runtime. These delays to the runtime can be calculated as follows:
((36 bytes + number of process data in bytes) * 8 * 10 nsec) + (2 * 1.76 µsec) = switch runtime
Example:
20 process data words + 4 PROFIsafe words => 48 process data bytes
((36 bytes + 48 bytes) * 8 * 10 nsec) + (2 * 1.76 µsec) = ((84 bytes) * 8 * 10 nsec) + (3.52 µsec)
Result: 10.24 µsec
The same calculation formula applies to the acyclic parameter channel.
According to the specification, the shortest Profinet I/O telegram must be 72 bytes. If the 36 fixed bytes are deducted from the 72 bytes, this leaves 36 bytes of process data. If less than 36 bytes of process data are now used, the Profinet I/O telegram will be filled with null bytes to enable it to be sent. For the calculation formula this means that for up to 18 process data words, the Profinet I/O telegram is always of the same length and the delay in runtime is therefore also the same.
Delays to runtime have also come about in the past through the use of external switches. Depending on the system setup, it may be worth setting up a mixed star / line topology.
The Profinet I/O 2-port communication module can be replaced by a Profinet I/O
1-port in existing systems without any limitations because it can also be operated with the older GSDML file. It's just the new functions of the 2-port communication module which can only be used with the new GSDML file. A message stating that the serial number of the communication module has been changed is only entered in the 9400 logbook once. This message would however also be entered in the logbook if a 1-port module were replaced by a new 1-port module.
