X20 system modules • X20 electronics module communication • X20CS1012
X20 system User's Manual 3.10
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4.18.3.8.6 M-Bus - Communication
Three important control and status bytes are provided in the B&R interface for communication with the M-Bus
slaves. For example the "MBusCommand" register can be used to switch UART on/off to increase the system's
energy efficiency.
Up to 8 cyclic input registers are registered depending on the configuration. Manually configured data must be
requested via the "MBusCommand" register. The "ValidDataByte" and "InvalidDataByte" registers can be used to
determine the quality of the value currently read.
Information:
The following section "M-Bus - Communication" is based solely on the B&R Standard interface.
4.18.3.8.6.1 M-Bus commands
Name:
MBusCommand
This register can be used to apply different commands to the module. The module only responds to positive edges.
Data type
Value
USINT
See bit structure.
Bit structure:
Bit
Name
Value
Information
0
Activate UART
0 → 1
Execute command
1
Read manually triggered values
0 → 1
Execute command
2
Acknowledge the "MBusState" register
0 → 1
Execute command
3 - 6
Reserved
0
7
Deactivate UART
0 → 1
Execute command
Bit 0 and 7
The level converter is switched on by default when the module boots. These bits can be used to switch it on or off
from the application to save electricity, for example.
4.18.3.8.6.2 M-Bus operation
Name:
MBusOperation
This register shows the user which task the module is currently processing. The LSB is always set when the UART
is active. Manual commands are indicated by an increase of one in this byte while being processed.
Data type
Value
USINT
See bit structure.
Bit structure:
Bit
Name
Value
Information
0
Inactive
0
UART
1
Active
0
-
1
Read values
1
Command being processed
0
-
2
Refresh/reset the "MBusState" register
1
Command being processed
1)
3 - 6
Reserved
0
0
Inactive
7
UART
1
Active
1)
Bit 2 is only set for one X2X cycle. Requesting this bit is not recommended when operating the module behind a bus controller.
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