8. Peripherals and Options
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● PROFIBUS-DPbus topology
485+
485-
CGND
485+
485-
RS485 bus
CGND
MD500
MD38TX1
MD500
MD38TX1
Set J3 to
match terminal
resistor
485+
485- CGND
485+
485- CGND
J3
Master
slave 1 slave N
J3
terminal
resistor
120Ω
terminal
resistor
120Ω
It is necessary to connect a matching terminal resistor to the end of PROFIBUS bus
and set DIP switch properly. The system PEs must be reliably grounded.
Length of communication cable between MD38DP2 and PROFIBUS-DP master varies
with different setting of baud rate of the master. Restrict communication cable lead
length strictly according to the Siemens DB9 standard. The following table describes
requirements on baud rate and communication cable lead length.
Baud Rate (Kbps) Max. Length of Lead A (m) Max. Length of Lead B (m)
9.6 1200 1200
19.2 1200 1200
187.5 600 600
500 200 200
1500 100 70
3000 100 Not supported
6000 100
12000 100
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