VEGA VEGAPULS 45 Profibus PA - Manual (Page 54)

54 VEGAPULS 42, 44 and 45 – Profibus PA
24908-EN-041227
Technical data
8.3 Data format of the output signal
Byte4 Byte3 Byte2 Byte1 Byte0
Status Measured value (IEEE-754 format, see below)
Status byte:
The status byte corresponds to Profile 3.0 „Profibus PA Profile for Process Control Devices“
coded. The status „Measured value OK“ is coded as 80 (hex) (Bit7 = 1, Bit 6 … 0 = 0).
Measured value:
The measured value is transmitted as 32 Bit floating point number in the IEEE-754 format.
Byte n Byte n+1
Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
VZ 2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0 2 -1 2 -2 2 -3 2 -4 2 -5 2 -6 2 -7
Sign
Exponent Mantissa
Byte n+2 Byte n+3
Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit Bit
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
2 -8 2 -9 2 -10 2 -11 2 -12 2 -13 2 -14 2 -15 2 -16 2 -17 2 -18 2 -19 2 -20 2 -21 2 -22 2 -23
Mantissa Mantissa
Formula: Meas. value = (-1) VZ • 2 (Exponent - 127) • (1 + Mantissa)
Examples: 41 70 00 00 (hex) = 0100 0001 0111 0000 0000 0000 0000 0000 (bin)
Meas. value
= (-1) 0 • 2 (130 - 127) • (1 + 2 -1 + 2 -2 + 2 -3 )
= 1 • 2 3 • (1 + 0.5 + 0.25 + 0.125)
= 1 • 8 • 1.875
= 15.0