Modbus Registers
Register loca ons and details can be found in the HM Con
fi
gurator so ware manual. The manual is included on the CD
and can be downloaded from www.micro
fl
x.com.
Write Locking
Wri ng to registers can be locked or write-protected a er se ng the con
fi
gura on to prevent unwanted changes to the
con
fi
gura on. Refer to the HM Con
fi
gurator so ware manual for details on write locking and unlocking registers.
Polled HART Devices Long Address Table, 700 - 747
Device ID informa on is read from each polled device using the devices polling address and HART command 0. The
reply to command 0 for each polled device is used to populate the long address table. When MicroLink-HM needs to
poll for the device variables, using HART command 3, this table holds the informa on needed to build the 5-byte long
address. Table values can be read using modbus-RTU command 3. Only the polled devices you have con
fi
gured will
contain valid informa on. The table is updated when the device address is unknown or a bad HART reply was received.
HART Device Polling Address Table, 748 - 755
The polling address for each polled device is stored in this table. Two polling addresses in each 16 bit register. If ad-
dress 0 is used then only one device can be polled and Device 1 should be set to 0. Address 0 is not valid in mul -drop
systems. For HART devices with HART revision 3 through 5 you should use polling addresses 1 - 15. Addresses 16-63
require HART revision 6 or higher.
Number of Decimal Places Table, 756 - 771
When storing the HART variable data in 16-bit modbus registers the maximum range is -32768 to 32767. To increase the
possible resolu on, the variable value read from the HART device is decimal posi on adjusted before being saved in the
16-bit register. When the register is read, the value must be corrected by the number of decimal places to produce the
correct value. The number of decimal places for each variable occupies 4-bits in the register with one register for each
polled device.
Setup Registers, 772 - 777
The MicroLink-HM con
fi
gura on can be changed using the HM Con
fi
gurator App or by wri ng to modbus registers using
modbus-RTU commands 6 or 16. Command 6 writes to a single register and command 16 writes to a range of modbus
registers. The con
fi
gura on register values are saved in nonvola le memory and are not lost when MicroLink-HM power
is removed.
6
