Installation and connection
31
TM800_D00165_00_M_XXEN/06.2015
4.2.3
BMS-bus connection
Communication between the TM800 alarm indicator and operator panel and other system compo-
nents takes place via two serial interfaces (internal and external BMS bus). These interfaces cables are
of two-wire design. See "BMS bus" instruction leaflet for more details about the BMS bus.
The number of bus devices is limited to 30. Install a DI-1PSM repeater if you want to use more devices
on the BMS bus. A DI-1PSM also is required when the BMS bus segment of 1200 m is exceeded.
4.2.3.1
Terminating resistor
The BMS bus must be terminated at both ends with terminating resistors of 120 Ω (0.4 W). One ter-
minating resistor is installed in each TM800 for the internal and external bus.
If several TM800 alarm indicator and operator panels are connected via the BMS bus, the terminating
resistors of the TM800 alarm indicator and operator panels which are not installed at the end of the
bus have to be switched off. The same applies to all other devices and modules that are not installed
at the end of the bus.
Use the DIP switches S1 and S2 to set the terminating resistor for the internal and external BMS bus:
S1 = external BMS bus; S2 = internal BMS bus. Factory setting: S1 and S2: off. The DIP switches are
located on the BM800 module adjacent to the interface terminals. Use the DIP switch to select on or
off position.
BMS-bus addresses
Be sure that the addresses of all devices connected to the bus are correctly assigned. Never assign
one address twice. Assign the addresses consecutively without any gaps. Bear in mind that each bus
requires one master. A device becomes a master by assigning address 1 to it. Address assignment
can be carried out via the menu of the TM800 alarm indicator and operator panel (see "Settings
menu 10: Interface" on page 65) or via the basic settings in the TMK-SET software.
Internal BMS bus
Select an address between 1 and 150 for the internal bus of the alarm indicator and operator panel
(factory setting: 1). The addresses 100…103 are reserved for special tasks (e.g. programming). This
setting can only be changed when the external bus has been switched off before. On the internal
BMS bus the baud rate is set to a fixed value of 9600 bits/s.
External BMS bus
Select an address between 1 and 99 for the BMS bus of the TM800 alarm indicator and operator pan-
el.
The external bus is primarily used for the connection of several TM800 alarm indicator and operator
panels. But also MK800 alarm indicator and test combinations and SMI472-12 signal converters can
be connected. Up to 99 devices can be connected.
The following applies to the external bus:
When the TM800 alarm indicator and operator panel is the only control device in the system,
address 1 (Master) is assigned to it.
Missing or incorrectly installed terminating resistors (e.g. in the middle of the
bus) will cause bus instability.
