Siemens SIMATIC NET PROFIBUS manual Bus terminal 12 M, Operator Controls

Passive Components for RS-485 Networks

Bus terminal 12 M

The 12M bus terminal is used to connect data terminal equipment (DTEs) with an RS-485 interface to the LAN cable.

It includes the following:

S1 modular terminal block with 6 terminals for conductors with a cross-sectional area <= 1.5 mm2 for connection of the incoming and outgoing LAN cable and, if necessary, the protective earth (PE)

SScrew down clamps for field contact

STwo switches:

Right switch (‘Termination‘), to terminate the end of an incoming, electrical segment (A1, B1) with the characteristic impedance (switch on). At the same time, the outgoing, electrical segment (A2, B2) is interrupted.

Left switch, used to set the range of the transmission rate 9.6 Kbps to 1.5 Mbps and 3 Mbps to 12 Mbps.

SA 1.5 m long tap line with a 9-pin sub-D male connector for direct attachment to a DTE.

The sub-D connector is plugged into the sub-D female connector of the DTE and secured by screws. The 12M bus terminal requires a current of 90 mA at a power supply of 5 V from the DTE between pins 5 (M5) and 6 (P5) of the sub-D male connector.

A maximum of 32 BT12M modules can be connected to one bus segment. If other components, such as repeaters are connected to a bus segment, this reduces the maximum number of 12M bus terminals.

9.6k to 1.5M		off
	R
3M to 12M	on	on
		Termination
	off

PE A1 B1 A2 B2 PE

Figure 4-30 Operator Controls

PROFIBUS Networks SIMATIC NET	4-53
6GK1970-5CA20-0AA1 Release 2 05/2000