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V2.01

25359_EDEBDA0279-2320-1_EN

Example 1: -12.5 decimal = 0xC1480000 hex

M: 24 bit-mantissa

E: Exponent with oset of 127

S: Sign for mantissa (S=1 neg.; S=0 pos.)

Address +0 +1 +2 +3

Format SEEEEEEE EMMMMMMM MMMMMMMM MMMMMMMM

Binary 1 1 0 0 0 0 0 1 0 1 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Hex C1 48 00 00

The byte sequence is dened as follows:

The byte with the “S sign bit” is transmitted over the bus as the rst byte.

The sequence of the oat bytes of the bus can be reversed, if necessary, using the device

parameter0xD02C (see table1).

The register value0xD02C in this case means:

 with 1 -> sign bit S in 1

byte (sequence as dened)

 with 0 -> sign bit S in 4

byte (sequence reversed)

The following information can be derived from this:

The sign bit is 1 => negative mantissa

The value of the exponent amounts to 10000010 bin or 130 dec.

This results in an exponent value of: 130 - 127 = 3

The mantissa has the following value: 10010000000000000000000

The decimal point can be found at the left end of the mantissa, preceded by a 1. This

position does not appear in the hexadecimal numeric notation. If you add 1 and set the

decimal point at the beginning of the mantissa, the following value is obtained:

1.10010000000000000000000

Now, the mantissa needs to be adjusted to the exponent. A negative exponent shifts the

decimal point to the left, a positive exponent shifts it to the right. Since the exponent is 3,

this is represented as: 1100.10000000000000000000

The number obtained corresponds to the binary oating-point number.

Binary digits to the left of the decimal point result in values > 1. In this example, 1100 bin

results in the number12 dec. {(1x23)+ (1x22)+ (0x21)+ (0x20)}

Binary digits to the right of the decimal point result in values < 1. In this example, .100.......

bin results in the number0.5 dec. {(1x2-1)+ (0x2-2)+ (0x2-3)+ (0x2-4)}

By adding the individual values, 12.5 is obtained. As the sign bit was set, it is a negative

value, -12.5. The hexadecimal number0xC1480000 thus corresponds to -12.5.

Data point description for the Modbus protocol

KBR multicomp F144-MS-1V1C1TI6RO-3 User Manual

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