The tag with Real and Long data type is 2 words (4 Bytes) format. It is allowed to change the reading order of the bytes on PLS by change the parameter in citect.ini file for MODNET protocol.
Modnet20 is specified for TSX Quantum PLC ranges. These protocol options will select the correct addressing modes, select certain INI values and other settings to provide compatibility with these devices without the need to set any other special parameters. Base on the default setting, some of parameters cannot be changed. Therefore, it is recommended to use Modnet protocol.

Please use the parameter to change the byte order for Real data type
[MODNET]
FloatMode = x where x is 0, 1, 2 or 3
Allowable Values:
0: Order of bytes = 1 0 3 2
1: Order of bytes = 3 2 1 0
2: Order of bytes = 0 1 2 3
3: Order of bytes = 2 3 0 1
Default Value: 0

In the MODNET protocol, LONG data types default to a simplified implementation, with a shortened range of 0 to 655,359,999 - mode 0. Mode 2 has the same range as mode 0, but with the register order swapped. Mode 1 supports the full LONG range of -2,147,483,648 to +2,147,483,647. Mode 3 has the same range as mode 1, but with the register order swapped.
When using the MODBUS protocol, CitectSCADA combines two registers to store a long data type in a PLC. The way in which it does this is defined by this parameter in the "citect.ini" file.

[MODNET]
LongDataType = y where y is 0, 1, 2 or 3
Allowable Values:
0 - implies 10,000 * low register + high register
1 - implies 65,536 * low register + high register
2 - implies 10,000 * high register + low register
3 - implies 65,536 * high register + low register
Default Value: 3


Last Revised: 09 Apr 2010
Original Author: EF
Public
All content © 1992-2010 Schneider Electric

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Legacy KB System (APS) Data: RESL201943 V1.0, Originally authored by KBAdPM on 04/13/2010, Last Edited by KBAdPM on 04/13/2010
Related ranges: PowerLogic SCADA 7.1