
Cabling and Wiring the System
6-8
SIMATIC 545/555/575 System Manual
Installing Series 505 Remote I/O Cables (continued)
Follow these guidelines when installing Series 505 RS-485 trunk and drop
line cabling.
• Measure the maximum length (consult Table 6-2) from the CPU to the
most distant tap. See Figure 6-2.
T T T
Maximum Trunk Length
T = Terminal Block
*A terminating resistor (shown in Figure 6-8) must be installed on the end terminal blocks. If only
one terminal block is used, a terminating resistor must be installed on that terminal block.
*Terminating
Resistor
T
*Terminating
Resistor
C
P
U
Figure 6-2 Maximum Trunk Length
• By using a T configuration (Figure 6-3), you can increase the total
trunk line length to twice the length specified in Table 6-2.
T T
T = Terminal Block
T TTTT
Total Trunk Line Length
C
P
U
*A terminating resistor (shown in Figure 6-8) must be installed on the end terminal blocks. If only
one terminal block is used, a terminating resistor must be installed on that terminal block.
Max. Trunk LengthMax. Trunk Length
*Terminating
Resistor
*Terminating
Resistor
Figure 6-3 T Configuration
Planning Your
Installation
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