Beckhoff EL3101, Документация

Страница: 42 / 229

Basics communication
EL31xx-00xx 42 Version: 5.9
Channel-based order
The CoE list is available in EtherCAT devices that usually feature several functionally equivalent channels.
For example, a 4-channel analog 0..10 V input terminal also has 4 logical channels and therefore 4 identical
sets of parameter data for the channels. In order to avoid having to list each channel in the documentation,
the placeholder "n" tends to be used for the individual channel numbers.
In the CoE system 16 indices, each with 255 subindices, are generally sufficient for representing all channel
parameters. The channel-based order is therefore arranged in 16
dec
/10
hex
steps. The parameter range
0x8000 exemplifies this:
• Channel 0: parameter range 0x8000:00 ... 0x800F:255
• Channel 1: parameter range 0x8010:00 ... 0x801F:255
• Channel 2: parameter range 0x8020:00 ... 0x802F:255
• ...
This is generally written as 0x80n0.
Detailed information on the CoE interface can be found in the EtherCAT system documentation on the
Beckhoff website.
3.6 Distributed Clock
The distributed clock represents a local clock in the EtherCAT slave controller (ESC) with the following
characteristics:
• Unit 1 ns
• Zero point 1.1.2000 00:00
• Size 64 bit (sufficient for the next 584 years; however, some EtherCAT slaves only offer 32-bit support,
i.e. the variable overflows after approx. 4.2 seconds)
• The EtherCAT master automatically synchronizes the local clock with the master clock in the EtherCAT
bus with a precision of < 100 ns.
For detailed information please refer to the EtherCAT system description .