Serial interface
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isoPV_D00024_02_M_XXEN/07.2018
7.3 BMS protocol
This protocol is an essential part of the Bender measuring device interface
(BMS bus protocol). 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 devices are slaves. It is important
that only one master is present in each network. All bus devices 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 commands. Bus address 1 must be assigned to the
master, thus to one of the isoPV devices.
7.3.1
BMS master
A master can query all warning and operating messages from a slave.
If the bus address 1 has been selected for one isoPV, the device automatically repre-
sents the master, that means that all addresses between 1 and 150 are cyclically scan-
ned via the BMS bus for alarm and operating messages. If the master receives no answer
from five subsequent addresses, the scanning cycle is started again. If the master recog-
nises incorrect answers from a slave, the fault message "Fault RS485" will appear on the
display.
Fault causes may be:
•
Addresses are assigned twice
•
A second master exists on the BMS bus
•
Interference signals occur on the bus lines
•
A defective device is connected to the bus
•
Terminating resistors are not activated
Fa u l t R S 4 8 5
R s = 0 1 1 k
W
.
H
Summary of Contents for ISOMETER isoPV with AGH-PV
Page 45: ...Operation and setting 45 isoPV_D00024_02_M_XXEN 07 2018 6 5 8 Diagram ISO ADVANCED ...
Page 47: ...Operation and setting 47 isoPV_D00024_02_M_XXEN 07 2018 6 6 4 Diagram COM SETUP ...
Page 57: ...57 isoPV_D00024_02_M_XXEN 07 2018 ...
Page 58: ...Coupled PV generators application example 58 isoPV_D00024_02_M_XXEN 07 2018 ...
Page 71: ......
