20
Installation and Operation Manual
X-DPT-Profibus-DP-Interface-eng
PN 541-C-068-AAG
November, 2008
The SPC3 also supports automatic baud rate detection. Therefore no hardware
means are necessary to select the required baud rate at the slave. Communica-
tion initiated by the master at a any of the supported baud rate values will
cause the Brooks Smart TMF series device to lock on to this baud rate after an
automatic search for it. Also, if no valid messages have been detected on the
network after a pre-programmed time out, the Brooks Smart TMF series will
switch to baud search mode, and search for the correct baud rate until found.
Table 3-3: Supported baud rate values.
Baud rate Max. response time Max. cable segment length
12 Mbaud 67 μsec (800 Tbit
*
) 100m/327 feet
6 Mbaud 75 μsec (450 Tbit
*
) 100m/327 feet
3 Mbaud 83 μsec (250 Tbit
*
) 100m/327 feet
1.5 Mbaud 100 μsec (150 Tbit
*
) 200m/655 feet
500 kBaud 200 μsec (100 Tbit
*
) 400m/1311 feet
187.5 kBaud 320 μsec (60 Tbit
*
) 1000m/3278 feet
93.75 kBaud 640 μsec (60 Tbit
*
) 1200m/3934 feet
45.45 kBaud
**
8.8 msec (400 Tbit
*
) 1200m/3934 feet
19.2 kBaud 3.125 msec (60 Tbit
*
) 1200m/3934 feet
9600 Baud 6.25 msec (60 Tbit
*
) 1200m/3934 feet
* Tbit is the time required to send 1 data bit, at the associated bit rate. Refer to standard
EN 50170.
** 45.45 kBaud is only used for Profibus-DP and Profibus-PA systems with coupling devices.
3.6 PROFIBUS NETWORK WIRING
3.6.1 Profibus network wiring requirements
The physical network connection with Brooks Smart TMF devices to be used
with Profibus-DP communication is based on RS-485. The standard EN 50170
specifies the type of cable to be used for this implementation. Table 3-4 below
lists the required cable parameters as specified by EN 50170.
The Profibus cable is a shielded twisted pair cable. The shielding must be
connected to protective ground (i.e. conductive housing on Brooks Smart TMF
series devices) in order to prevent EMC interference from entering the device.
Table 3-4: Profibus cable parameters
Parameter Line type A Unit
Impedance 135 to 165 [Ω]
Capacitance per unit length < 30 [pF/m]
Loop resistance 110 [Ω/km]
Core diameter 0.64 [mm]
Core cross section > 0.34 [mm
2
]
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