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MbCmd defines, what Modbus commands are executed on the Bus, when, and what Modbus Configuration to use for them. The configuration is very flexible and allows complex setups, that include executing different commands at individual intervals or times or using multiple different Modbus parameters to address incompatible Slaves on the same installation. Any Modbus command can be sent, including writing registers or diagnostic messages.
The command is entered in Hex and without any check sums and is 6 bytes long (12 hexdigits). The default value is
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010300000003, it consists of 4 hex parts: 01, 03, 0000, 0003
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0x01
Address of the Slave Device. 1 byte: often 01 new devices
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0x03
What kind of Modbus Register to read. 1 byte. 03 stand for Holding Register.
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0x0000
Number/address of the first register to read. 2 bytes. Many devices have some value to read out at 0000.
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0x0003
Number of consecutive registers to read from the first register. 2 bytes. This would read the registers #0, #1, and #2 in one command.
The default value of 0 0/5 * * * *:R,9600,8N1:010300000003 shows a very basic example with a single entry executed every 5 minutes using Modbus RTU to read 3 consecutive holding registers from a single slave device.
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