FieldServer FS-8700-01, FS-8700-08 Appendix A.5. Connection to York Modbus Microgateway

FS-8700-01_Modbus_RTU_(T28700-01) Driver Manual Page 18 of 21

Transferring 32 bit values with two registers

If a Modbus Server sends two consecutive registers to the FieldServer representing either a floating point value or a 32 bit integer value, the FieldServer can combine and decode these registers back into their original format. To do this, the user must read the registers into an integer data array, and then use the Moves function to move the data to a floating point or 32 bit integer data array. The “function” field in the move must be populated with the correct move function required. Details of the available function fields are listed in the FieldServer configuration manual along with a more detailed explanation of moves. Note that functions also exist to split a floating point value into two integers using the reverse operation.

A diagrammatic representation of this process is depicted below:

Modbus

Device

Two 16 bit integers polled:

e.g: 40001, length 2 Together, they combine to form a 32 bit IEEE Floating point number.

Modbus

Source Data Array

-------------------------

Offset 0: 40001

-------------------------

Offset 1: 40002

-------------------------

Special	Float Data Array
	-------------------------
Move	Offset 40: Float value
	-------------------------

Sensible data

Unreadable

content

The example below shows how a floating point value is retrieved from two Modbus registers that were placed in an integer data array.

Example
Data_Arrays
Data_Array_Name,		Data_Format,	Data_Array_Length
DA1,		int16,	20
DA2,		float,	10
Moves
Function,	Source_Data_Array,		Source_Offset,	Target_Data_Array,	Target_Offset
2.i16-1.float-sw,	DA1,		0,	DA2,	6

This Move will cause two integers at offsets 0 and 1 in the integer Data Array DA1 to be copied to offset 6 in the float Data Array DA2. In the process of copying the values, the integers will be combined and treated as an IEEE 32 bit floating point number.

Appendix A.5. Connection to York Modbus Microgateway

If connecting the FieldServer to a York Modbus Microgateway, the Node_ID of the Microgateway is defined by the address DIP switches. If switch 4 is set to ‘On’ and the other switches are set to ‘off’ then Node_ID of the Microgateway is ‘247’, the parity is ‘Even’, and the stop bits are 1. Other Node_ID combinations can be found in the York Modbus Microgateway Installation Manual.

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