PI E-727, Руководство пользователя, Страница: 148 / 240

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 148 / 240
Phone +49 721 4846-0, Fax +49 721 4846-1019, Email info@pi.ws , www.pi.ws
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 bits of CTR2 (bit 4 through bit 7) are used by the sender of a data stream. The bits have the
following meaning:
DataCtrl (bit 5, bit 4):
(0, 0) = No slow data transferred. The values of bits 6 und 7 (TwoBytes-Flag und
SToggle-Flag) are invalid. The bytes of data segment 2 ares used for cyclic flag transfer,
for example OnTarget flags from PI-controller to host or Servo mode change bits from
host to PI-controller.
(0, 1) = Initialize stream transmission on receiver side. SToggle-Flag is transferred so
that the RToggle-Flag on receiver has a definite initial value. No slow data transferred.
The bytes of data segment 2 are used for cyclic flag transfer.
(1, 0) = A data fraction of the stream is transmitted by data segment 2. The TwoBytes-
Flag und SToggle-Flag are valid and must be evaluated by the receiver.
(1, 1) = Last data fraction of a stream is transmitted by data segment 2. The receiver has
the possibility to generate an interrupt so that the receiver FIFO can be read out. The E-
727 will also set this control value when large data blocks are transferred or when the
speed is high before the complete data block was transferred (before terminating line
feed) so that one large block is split up in a number of smaller data blocks.
TwoBytes (bit 6):
0 = One data byte is transferred by data segment 2. The second byte of data segment 2
is invalid.
1 = Two bytes are transferred by data segment 2.
The TwoBytes-Flag is valid only when bit 5 is “1” (DataCtrl = (1, 0) or DataCtrl = (1, 1)).
SToggle (bit 7):
In principle the SToggle bit is just the lowest bit of a data counter.
The toggle bit is used to show the receiver that a new fraction of data is sent. The
sender shows this by inverting the SToggle value each time when a new data fraction is
loaded from the sender FIFO to the transmission register. When the receiver detects
that the SToggle changed its value compared with the last data segment 2 transfer cycle
then it must save the received data.
When the receiver sends an acknowledge it will reflect the very last SToggle value. For
this purpose the the RToggle bit of the PID/ST byte is used (see description of the
PID/ST byte).
The SToggle-
Flag is only valid when DataCtrl ≠ (0, 0).
For the acknowledge response the lower bits of the PID/ST byte are used.
PID ST
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
0 0 0 1 0 CRCError RToggle ACK