Allen-Bradley 857-VPA3CG, Руководство пользователя, Страница: 10 / 14

10 Rockwell Automation Publication 857-UM003B-EN-P - December 2017
857-VPA3CG Profibus DP Option Module
Specifications General
PROFIBUS Cable
PROFIBUS devices are connected in a bus structure. Up to 32 stations (master or
slaves) can be connected in one segment.
The bus is terminated by an active bus terminator at the beginning and end of
each segment (see
Cabling Bus Termination on page 11 ). To ensure error-free
operation, both bus terminations must always be powered. When more than 32
stations are used, repeaters (line amplifiers) must be used to connect the
individual bus segments.
The maximum cable length depends on the transmission speed and cable type.
The specified cable length is increased by the use of repeaters. The use of more
than three repeaters in series is not recommended.
Table 2 - PROFIBUS DP Connections
Interface 9-pin DSUB connector (female)
Transfer method RS-485, Half-duplex
Transfer cable Twisted-pair (1 pair and shield)
Electrical 500V DC
Safety Meets standard EN50178
Table 3 - PROFIBUS Communication Data
Communication mode PROFIBUS DP
Communication parameters
Address 1…126
Baud Rate 9.6 kBaud...12 MBaud
Table 4 - Line Parameters
Parameter Line A Line B
Impedance 135...165 Ω (3…20 MHz) 100…130 Ω (f> 100 kHz)
Capacity < 20 pF/m < 60 pF/m
Resistance 110 Ω/km —
Wire gauge > 0.64 mm (22 AWG) > 0.53 mm (24 AWG)
Conductor area > 0.34 mm
2
(22 AWG) > 0.22 mm
2
(24 AWG)
Table 5 - Line Lengths for Different Transmission Speeds
Baud rate (bBit/s) 9.6 19.2 93.75 187.5 500 1500 3000…12,000
Length Line A (m) 1200 1200 1200 1000 400 200 100
Length Line B (m) 1200 1200 1200 600 200 — —