Festo Кабели и принадлежности - Manual (Page 72)

5. Data structure
5−14
Festo P.BE−SPC200−COM−CANDN−EN en 0511a
The handshake cycle for reading data PLC { SPC200
The Command Message is parametrized by the user program.
The transmission cycle begins when the LOAD signal is set by
the PLC (bit 7 in byte 0 of the Command Message). The
SPC200 accepts the data, checks them for plausibility and
limit values and, if necessary, generates a fault message. With
LOAD COMPLETE, the SPC200 informs the PLC that the deĆ
sired data are available and the PLC can now accept the data.
A transmission cycle is concluded when the user cancels the
LOAD signal. During the handshake cycle no update data are
transmitted.
The following diagram explains the correlation:
To SPC200:
To PLC:
PLC:
SPC200:
1 2 3
1
SPC200 accepts the Command Message
2
SPC200 gives the Response Message
3
SPC200 sends the requested data or, if applicable, the
fault protocol
Only one axis or only one activity can be triggered with a
write or read command. If, e.g. the actual positions of four
axes are to be read, four appropriate read commands must
be issued one after the other, i.e. four transmission cycles are
necessary.