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User Manual
E727T0005, valid for E-727
BRO, 2019-06-28
Physik Instrumente (PI) GmbH & Co. KG, Auf der Roemerstrasse 1, 76228 Karlsruhe, Germany
Page 147 / 240
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email
Transport Layer
Data Segment 1
Data segment 1 transports the fast 32-bit data. The number of data words which is currently sent is
coded by the CTR2/CNT1 byte:
CTR2
CNT1
Bit 7
Bit 6
Bit 5 Bit 4 Bit 3
Bit 2
Bit 1
Bit 0
SToggle
TwoBytes DataCtrl
DS1 Data Word Counter
The upper part CTR2 (bit 4 through bit 7) of the CTR2/CNT1 byte controls the transmission through
data segment 2 and will be explained in the next section.
The lower part CNT1 (bit 0 through bit 3) counts the number N of currently transferred 32-bit data
words. The value N can be any number between 0 and 15 so that the position data of up to 15 axes
can be transferred. Note that with E-727, the behaviour is as follows:
In the first data packet sent by the slave (E-727) after power-on, the number of axes
is 0.
In all subsequent data packets, the slave sends data for the same number of axes as
used by the master in the previous cycle, provided that the number of axes is less
than or equal to 4. Should values for more than 4 axes be sent by the master, the
slave limits the response to 4 axes.
Data Word 1
Data Word 2
…..
Data Word N
4 Byte
4 Byte
4 Byte
4 Byte
The 32-bit data words are send with the highest bit first and the lowest bit last. The following table
shows one 32-bit data word of the data stream:
Data Word i
b31
b30
b29
b28
……
b1
b0
Data Segment 2
Data segment 2 is used for slow transfer of GCS commands and their responses. The length of data
segment 2 is 2 bytes. When no data is transmitted by data segment 2 then it is used for the cyclic
transfer of flag bits. In general a GCS command and its response is longer than 2 bytes and so
multiple transfer cycles are needed to transfer a complete command or a command response. In
the following, GCS commands or command responses which are transferred by data segment 2 are
referred to as “data stream” whereas the part of a GCS command or of a command response
which is transferred during one transfer cycle is referred to as “data fraction”.
Both the host and the PI-controller need an additional logic to process data segment 2. In the
following, these control units are called sender and receiver. The two transfer directions from host
to PI-controller and from PI-controller to host are working completely independent from each
other. The architecture of sender and receiver can be the same on host and PI-controller side.
For controlling the transmission via data segment 2 the following control and status bytes are
transferred. See also next section for the transport layer flow charts (p. 150):