
COMMUNICATION
MULTI GAUGE CONTROLLER
Note
: The MG
enables communication with a MASTER device with a write/read speed not
exceeding
frames/second.
. . .
CONNECTION PARAMETERS
PARAMETER
VALUE
Data bits
Parity
None
Stop bits
Flow control
None
Baudrate
(default)
Table . : Connection parameters
. . .
FRAME FORMAT
Typical data exchange consists in sending a query from the MASTER device and a response to this
query from the SLAVE device.
A typical message in both directions should consist of the following information:
Start
Device address
Function code
Data
CRC
EOT
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Table . : Modbus RTU frame format
•
Start
- is an inactivity period, which equals to at least . times of the transmission time of a
single character. E.g. for baudrate
bps with start bit, stop bit and bits of data, the
Start time is . ms. Very often Start time results from the EOT time of the previous frame.
•
Device address
- unique -byte device address set on the jumpers in the rear panel (chapter
. . ). Address is a broadcast address.
•
Function code
- -byte code unequivocally identifying action to be executed by the Slave
device.
•
Data
- length and type of data depends on the function code. Usually, a data segment will
contain the parameter address and number of data to read or write.
•
CRC
- -byte checksum used to check the correctness of data in a communication frame. Cal-
culation of checksum see chapter . . . .
•
EOT
- the segment at the end of a frame showing to the slave devices that a new message
will be transmitted next. As a standard, at least . times of the transmission time of a single
character.
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