Mounting and Installation
© Siemens AG 2002 All Rights Reserved 6NH7811-0AA22
MD2 Modem (07/2002)
2-25
Standard cable 6NH7701-4DL is used for connecting the DTE (e.g. TIM) to the first
MD2. There is no prefabricated cable for the connection to the next modems.
However, one can be built using standard components from the SIMATIC S7
product catalog. The same components can be used as those for making an MPI
connection. 6XV1830-0AH10 is recommended for the cable, and 6ES7972-0BA12-
0XA0 for the plug. The RS485 terminating resistor for the line can be switched on
this plug if required.
The table on the next page shows how several MD2s can be connected in parallel
using the various cable sections.
!
Important
Do not forget to activate the terminating resistor for the RS485 bus with the
slide-switch on the last plug (see Fig. 2-13)!
The connection to the dedicated line is made through overvoltage protection
modules LTOP1 or LTOP2. The diagram shows the various connections possible
for 1 x 2-wire, 1x 4-wire or 2 x 2-wire terminal point for each MD2 modem. The 5-
pin DIL switch accessible from above on the modem is used to make the
appropriate setting for the type of terminal point (see Table 2-10).
RS485 Operation of the MD2
When connecting several MD2s in parallel through the RS485 interface, the
following should be taken into consideration in making the settings on the MD2
modem:
1) The MD2 modem must be set to the "Interface with RS485" operating mode
using the 10-pin DIL switch (see Fig. Fig. 2-4).
2) The RS485 interface must also be activated with the 4-pin DIL switch
accessible from below (see Fig. 2-6).
3) If the DTE connected to the MD2 modem is a SINAUT ST7 TIM, follow the
instructions in the SINAUT ST7 Manual, Chapter 5.1.4.
!
Important
If the MD2 is operated via its RS485 interface there is no communication possible
with the MD100 modem, that otherwise is compatible. The compatibility is only
valid if the RS232 interface of the MD2 is used.
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