Siemens 6RA7086-6KS22 Operating Instructions Manual page 206

Start-Up
Transmission rates and bus cable lengths:
Transmission rate
To ensure proper functioning, both ends of the bus cable must be terminated by a terminating
resistor (121Ω metal film resistor, +/- 1%, 0.25W).
The DeviceNet cable screen should be earthed at ONE point (e.g. at the power supply). Earthing
the screen at several locations can produce ground loops and cause malfunctions.
Telegrams transmitted via DeviceNet have the same useful data structure as those used in CAN
Bus communication.
A CAN telegram comprises the protocol header, CAN identifier, up to 8 bytes of useful data and the
protocol trailer.
The methods applied for DeviceNet transmissions allow useful data of any length to be transferred.
Data which are longer than 8 bytes can be transmitted in fragmented form (in several consecutive
telegrams).
PZD object (process data)
Both control words and setpoints as well as status words and actual values (process data) are
transmitted by means of DeviceNet I/O message connections. The number of process data to be
transferred (4, 8 or 16) depends on which DeviceNet I/O assembly instance has been selected.
The quantity of process data transmitted by the drive can differ from the quantity received.
Options for defining the number of PZD:
"Consumed Connection Path" with "Poll I/O" (direction: Master -> drive)
-
"Produced Connection Path" with "Poll I/O" (direction: Drive -> master)
-
"Produced Connection Path" with "Bit Strobe I/O"
-
The meaning of each process data word is determined by the assignment of connectors
parameterized in the drive (see function diagrams in Section 8, particularly "Data exchange with 1
nd
and 2 CB"). Process data can be exchanged between the SIMOREG and CBD 6x per line period,
i.e. every 3.3ms at 50Hz, but is dependent on the data exchange mode via DeviceNet. For further
details, see also "Information about PZD transmission" in Section 7, "Sequence of operations for
starting up CAN Bus boards".
Information about PZD transmission:
The low-order byte or word is always transferred before the high-order byte or word.
Control word 1 must always be sent as the first PZD word. If control word 2 is also used, this must
always be sent as the 4
Bit10 in control word 1 ("control requested") must always be set or else no new setpoints will be
accepted from the drive.
The second PZD word should normally contain the main setpoint.
7-48
Max. cable length
(thick cable)
125kbaud 500m
250kbaud 250m
500kbaud 100m
U712 = 120 ... 4 PZD (control word and setpoints)
U712 = 121 ... 8 PZD (control word and setpoints)
U712 = 122 ... 16 PZD (control word and setpoints)
U711 = 170 ... 4 PZD (status word and actual values)
U711 = 171 ... 8 PZD (status word and actual values)
U711 = 172 ... 16 PZD (status word and actual values)
U711 = 170 ... 4 PZD (status word and actual values); cannot be changed
th
PZD word.
Spur line length (thin cable)
Maximum Cumulative
6m 156m
6m 78m
6m 39m
SIEMENS AG
SIMOREG DC Master
05.05
st
6RX1700-0AD76
Operating Instructions