Two transfer formats are supported for reading and writing long integer and floating point values: standard Modicon Protocol and Daniel extensions.
The standard Modicon protocol supports the transfer of each floating point or long integer value as a pair of consecutive 16-bit analog registers.
Daniel extensions to Modbus commands 3, 4 and 16 allow the transfer of each floating point or long integer value as a single 32-bit register.
SIXNET Modbus Slave Operation:
IPm, SixTRAK and VersaTRAK stations can be configured to use Daniel extensions or the standard Modicon protocol when responding to Modbus commands for long integer or floating point registers.
SIXNET Modbus Master Operation:
IPm, SixTRAK and VersaTRAK stations can be configured to use Daniel extensions or the standard Modicon protocol when sending Modbus commands to read or write long integer or floating point registers. Daniel extension support can be enabled or disabled on a per-I/O transfer basis. When Daniel extension support is disabled, floating point and long integer registers are transferred as a pair of analog registers.
When configuring your SIXNET station, do not check the "Use Daniel Extension" checkbox if your Modbus master or slave device uses the Modicon (two 16-bit registers) method.
Note: EtherTRAK high-speed counter modules (ET-8CNT) do not support Daniel extensions. The 32 bit registers in this module are each read as a pair of 16 bit registers only.
Refer to the following topics for more information on the two transfer modes.
Transferring Longs and Floats as a Pair of Analog Registers (Modicon format)
Transferring Longs and Floats as 32 Bit Registers (Daniel extensions)