ProSoft Technology PS-QS-1x10-0781 - Manual (Page 24)

FieldServer Configuration Manual Page 24 of 90
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5.2.2 Converting two Integers to a Float.
Data_Arrays
Data_Array_Name , Data_Format , Data_Array_Length
Source_DA
, Uint16 , 200
Target_DA , Float , 200
Moves
Function , Source_Data_Array , Source_Offset , Target_Data_Array , Target_Offset , Length
Join_Float , Source_DA , 0 , Target_DA , 40 , 5
5.2.3 Using Moves to pack and unpack bits to or from a Register
A register provided by a device often consists of a set of binary values packed together for efficient data transfer.
These registers are normally 16 bits in size, but may also be 8 or 32 bits long. Since a register is read as an analog
value by most protocols, these binary values need to be extracted out of the register into a bit data array before
they can be read as useful data. The Bit_Extract Move function has been created for this purpose.
The Bit_Pack function can be used to pack bits into a register.
The Bit_Move function allows the user the ability to extract a group of bits in one register and place them singly
into another register.
The Bit_Offset keyword can be used to start moving a group of bits from a specified offset within the register. This
keyword may also be used in conjunction with the Bit_Extract and Bit_Pack functions to specify the first register
offset to Extract or Pack.
The Length keyword will always specify the number of bits to be moved in the move operation when using these
three functions. If the length keyword is not used, then only one bit will be moved.
Note: The Data_Array_Type being used in source and target Data_Arrays can produce varying results and care
should be taken to use the correct type. For example, when using the Bit_Extract function, it makes sense to use
Byte, UInt16, or Uint32 source Data_Array_Types to extract 8, 16 or 32 bits per register respectively. It also makes
sense to use the Bit Data Type for target Data_Array_Type. However, the FieldServer will allow other types to be
used and follow a routine choice of conversion that may not be considered predictable to all users. For example, if
the Float Data_Type is used as a source type in Bit_Extract, 32 bits per register will be extracted according to the
rounded Integer number being represented in the Float Register. If the Float Data_Type was used as a target type
in Bit_Extract, then each float register would store one binary value and would only ever represent 1 or 0.
Ten 16 Bit Integers are taken
from Source_DA and
combined in two’s to make
up 5 floating point values Length refers to the data type referenced in the Function.
eg: If n is the value shown in Length, then:
Join_Float creates n Floats
Split_Float disassembles n Floats
Join_Int16 Creates n Integers
Bit_Extract extracts n Bits, etc