Appendix A. Modbus application
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Appendix A. Modbus application
The protocol Modbus is applied for device network communication in the Master, Slave and Slave
Ext modes.
Table list:
– A.1 – Modbus functions
– A.2 – Modbus errors
– A.3 –
RS1 (PC) interface
parameters
– A.4 –
Settings
tab parameters
– A.5 –
Date and time
pane parameters
– A.6 – Digital key
– A.7 –
Channels
tab parameters
– A.8 –
Analog inputs
tab parameters
– A.9 –
View data
tab and other operation parameters
– A.10 –
Analog inputs
– Measured values
– A.11 –
Analog inputs
– Adjustment result
Specifics of the protocol application in the device:
– The broadcast address 0 and addresses greater than 247 are not answered by the device.
– The response time should be calculated as follows:
1 2x transmission time (depends on the data transfer rate in the channel) + 2x delay
time for data transfer in the GSM channel when working via modem (set in configuration).
– The command execution time can be up to 30 s (time to delete a file of 1GB).
– If the command cannot be executed within 1 second, error 07 (
) will be returned. Until the
current command execution is completed, further commands will be responded with the error 08
and the current function code.
– It is not possible to cancel the execution. After the command execution, the communication
continues as usual.
– When attempting to write “read only” parameters or access nonexistent registers with the
function 16, the error 01 will be returned.
– When attempting to read “write only” parameters or access nonexistent registers with the
function 03, the error 02 will be returned.
– When attempting to read (03) or write (16) several parameter groups, the error 03 will be
returned.
– The parameters can be requested with one command and only in groups represented in
. They cannot be requested individually, except the parameters of the tab
View data
) which can be requested individually or with one command in a group of up to
40 consecutive channels, beginning from any.
– If the configurator is connected to the device over USB, the requests of the configurator
connected to RS1 will be answered with the error 09.
– The logger cannot to send or receive packets of the size multiple of 64 bytes over the USB
interface. To solve this problem, it is recommended to transmit only odd-length packets over USB.
When transmitting an even-length packet, an extra byte 0x00 must be added at the end of the
packet (after CRC).
Table A.1 Modbus functions
Code
Name
Description
03 (0x03)
Read Holding
Registers
Read the contents of a contiguous block of holding
registers
04 (0x04)
Read Input Registers
Read from 1 to 125 contiguous input registers
16 (0x10)
Write Multiple
Registers
Write a block of contiguous registers (1 to 123 registers)
17 (0x11)
Report slave ID
Reading the device name and the firmware version
