PROFINET communication with encoTRive
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5.3 Access to parameters via PKW channel
If a PKW channel is used, then this occupies the first 8 bytes of the telegrams, which
are cyclically exchanged between control and encoTRive. The encoTRive recognizes
as part of the controller configuration, whether the system is working with or without
PKW channel.
The control generates a command to read or write a parameter. The command
contains the access type, parameter number, index and the value to be written if
applicable. The command must exist until the encoTRive has sent the relevant
response and the control has received it.
As both PKW telegrams are sent cyclically, the assignment of command to response
is only possible via the parameter identifiers and index if applicable.
Parameter values can be written and read and the parameter description read via the
PKW. In this case, the following conventions apply:
● In the case of simple parameters, 0 is always used as the subindex.
● Array parameters start with subindex 0
● Parameter numbers and parameter values are in Big Endian Format: An integer
16-bit value 0x1234 is transmitted so that 0x12 is sent first, followed by 0x34. In the
case of a 32-bit value 0x12345678 the value 0x12 appears at the lowest address in
the telegram first of all, followed by the values 0x34, 0x56 and 0x78.
● The initiative always comes from the IO controller (no spontaneous messages)
The following must be observed for command/response processing:
● Command and response always relate to a parameter, a parameter description
with corresponding index.
● Always retain the command until the encoTRive has sent the relevant response.
● encoTRive sends the response until the control sends a new command.
● encoTRive automatically updates the values if the same command is repeated.
PKE
(Parameter identifier)
Table 2: PKW range
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