KUNBUS-COM EtherCAT
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Protocol
KUNBUS has defined a separate protocol for the data exchange via
the synchronous serial interface. This protocol allows you to perform
various read and write access operations. Here, the Master first
always sends a transmission block with at least 5 bytes. The first 3 to
5 bytes of this transmission block consist of meta data (target
address, etc.). Depending on the access type, another transmission
block of variable data length follows the first block. Write and read
access to the memory register of the module is performed. Only
memory registers that have been enabled can be written or read, of
course. The following areas cannot be written:
Input data areas:
– Fieldbus
– SDI
– DPR
Output data areas:
– Fieldbus
– SSC
– SDI
– DPR
When writing to the SSC input data area, the time monitoring is reset
for this area (see Valid Time, Section "Data Broker [
}
20]").
Read access to the DPR areas is fundamentally not possible. The
module can never be in SPI/SSC mode and DPR mode at the same
time. Consequently, access to DPR areas would make no sense.
The various access types are explained below.
Writing 1 byte
This access type is used if 1 byte is written to a memory register of
the module by the Master.
The Master first sends a transmission block with a fixed length of 5
bytes, which have the following content:
Transmission block with fixed length
Command
code
(1 byte)
Address area
(2 bytes)
Data area
(1 byte)
Mask area
(1 byte)
Description
0x01
0x0000-0xFFFF
0x00-0xFF
0x00-0xFF
WRITE_LOW_BYTE
0x02
0x0000-0xFFFF
0x00-0xFF
0x00-0xFF
WRITE_HIGH_BYTE
0x00
0xXXXX
0xXX
0xXX
NO_OPERATION*
Theoretically, you could use all memory register addresses between
0 and 0xFFFF. In practice, however, the write access is limited to
registers that are enabled for this purpose. The byte can be written to
the high or low byte position of the 16-bit wide register by selecting
Components
