Bender ISOMETER IRDH375, Manual

Page: 71 / 100

Serial interfaces
72 IRDH375_D00124_05_M_XXEN/01.2020
The number of bus nodes is restricted to 32 devices. When more devices are
to be connected, Bender recommends to use an RS-485 repeater DI1.
7.4 BMS protocol (IRDH375B)
This protocol is an essential part of the Bender Measuring Device Interface.
Data transmission generally makes use of ASCII characters.
Interface data are:
 
Baud rate: 9,600 baud
 
transmission: 1 start bit, 7 data bits, 1 parity bit, 1 stop bit (1, 7, E, 1)
 
Parity: even
 
Checksum: sum of all transmitted bytes = 0 (without CR and LF)
The BMS bus protocol works according to the Master/Slave principle. That
means that one device represents the Master while all other bus nodes are
Slaves. It is important that only one Master is present in each network. All bus
nodes are identified by a unique address. The Master scans all other devices
on the bus cyclically, listens to their signals and then carries out specific com-
mands. Bus address 1 must be assigned to the Master, thus to one of the
IRDH375B devices.
DI1
1
32
33 64