Rockwell Automation 1788-EN2PAR EtherNet/IP and ControlNet to PROFIBUS PA Linking Device User Manual - Manual (Page 21)

Rockwell Automation Publication 1788-UM058B-EN-P - September 2014 21
Installation Chapter 1
Cable Type and Minimum Requirements
Per section 12.8.2 of IEC61158-2 (Physical Layer Specification), the PROFIBUS
PA cable must meet the following minimum requirements:
• Impedance at 31.25 kHz of 100
Ω
± 20%
• Maximum attenuation of 3 dB/km
• Conductor cross-sectional area of 0.8mm
2
(18 AWG)
• Shield coverage of at least 90%
• Maximum DC resistance of 24
Ω
/km per conductor
• Maximum capacitive unbalanced to the shield of 4nF/km
Cable Color Coding
Per section 12.8.8 of IEC61158-2 (Physical Layer Specification), the color code
of the PROFIBUS PA cable must match the descriptions in the following table.
Termination Guidelines
Terminate the PA bus cable at the beginning and end of the cable. You can set the
linking device to be internally terminated. If the architecture allows it,
terminators can be placed at different locations. See
Appendix B for architectures
and their correct termination locations.
Verify that junction boxes are not terminated internally. More than two
terminators will cause the communication signal to become slewed and
attenuated, which causes the signal to become unreadable.
Per section 12.8.6 of IEC61158-2 (Physical Layer Specification), terminator
impedance is equal to a 100
Ω
resistor in series with a 1
μ
F capacitor.
Cable Strand Color
PA cable positive (+) Red
PA cable negative (-) Green
Non-IS PA cable Black
IS PA cable Blue or blue/black