Rs485 Interface; Repeater Interface - Relay PW100 User Manual

PW100

3.3 RS485 Interface

A 2-wire RS485 interface will be connected to the RS485 terminals (A = + and B = -). Please note that this is
a transparent interface without addressing on the RS485 bus. The direction control of the half-duplex 2-wire
connection is realized that the PW100 is passive in the idle state (receiver on, transmitter off) and becomes
on transmitted data from M-Bus meters (receiver off, transmitter on). The level converter remains active on
the RS485 for approximately 50ms after the last transmitted space (0-Bit) of the slave. The master software
should not start a new request to the connected meters during this period.
The RS485 bus is not terminated in the PW100. If a termination is required, an appropriately dimensioned
external resistor, e.g. 120Ω can be connected between terminals A + and B-.

3.4 Repeater Interface

The PW100 can be used as a so-called Repeater, as a network extension for existing M-Bus systems, if the
maximum number of meters or the maximum cable length has been exceeded for the installation. Up to 100
devices and up to 4km cable (1 x 2 x 0.8 JYSTY) at 2400 baud transmission speed can be connected to a
repeater.
The M-Bus line of the existing master or level converter is connected to the terminals labelled with M-Bus
Repeater. The polarity does not matter - as usable and standardized for M-Bus slaves. The signal at the
M-Bus output of the PW100 is reconditioned to connect a complete M-Bus network. An almost unlimited num-
ber of repeaters can be cascaded or connected in parallel due to the automatic measurement of the maximum
transmission speed and the recovery of bit times (bit recovery) by the digital repeater. This allows nearly
unlimited M-Bus networks.
PW100 · User Manual Version 1.0 - 11/2020 7