Mapping DeltaV data to Modbus input and holding registers

Modbus input registers and holding registers are both 16-bit values read from or written to the Modbus device. The Serial Card treats both register types the same with regard to data mapping.

Table: Mapping DeltaV Data Types to Input and Holding Registers
DeltaV Data Type	Mapping Method
Boolean	The card sets the Modbus register to 0 if the Boolean has a value of 0 and to 1 if the Boolean has a value of 1.
Discrete, 8-bit signed integer and 8-bit unsigned integer	The card maps the DeltaV value to the lower eight bits in the Modbus register and sets the upper eight bits to 0.
16-bit signed integer and 16-bit unsigned integer	The card maps all 16 bits of the DeltaV integer directly into the Modbus register.
32-bit signed integer and 32-bit unsigned integer	The card maps the DeltaV value to two consecutive Modbus registers. The first is the least significant word, and the second is the most significant word.
Floating point	Floating point values are stored on Modbus PLCs in IEEE format in two consecutive registers with the first being the least significant word and the second being the most significant word. Therefore, the Serial Card maps DeltaV floating point values to two consecutive Modbus registers. The first register contains the least significant word, and the second contains the most significant word.
String	The Number of values field indicates the size of the string. The Serial Card maps the string to consecutive Modbus registers starting with the start register configured for the dataset. The first Modbus register contains the first two characters of the string with the high order byte containing the first character and the low order byte containing the second character. The card maps the remaining characters in the string to ascending Modbus registers with the characters in the same order in the registers.