Michell Instruments Liquidew EExd, User Manual

Page: 81 / 90

Liquidew EExd User’s Manual
Michell Instruments 73
APPENDIX G
Examples of floating point to HEX are shown below.
1) +10.3
sign bit = 0
Exponent = 3, therefore exponent field = 127 + 3 = 130, and bits 30 to 23 = 1000 0010
Mantissa = 1.2875 which in binary representation = 1010 0100 1100 1100 1100 1101
Adjusting the mantissa for the exponent moves the decimal point to the right if positive
and to the left if negative.
As the exponent is = 3 then the mantissa becomes = 1010 0100 1100 1100 1100 1101,
therefore:-
1010 = (1x23) + (0x22) + (1x21 ) + (0x20) = 10 and
0100 1100 1100 1100 1101 = (0x2
-1
) + (1x2
-2
) + -- + (1x2
-20
) = 0.3
Therefore the word value = 0100 0001 0010 0100 1100 1100 1100 1101
= 4124CCCD
Consequently, for sensor 1 register 0001 = 4124 and register 0002 = CCCD
2) - 0.0000045
sign bit = l
Exponent = -18, therefore exponent field = 127 + (-18) = 109, & bits 30 to 23 = 0110 1101
Mantissa = 1.179648 which in binary representation = 1001 0110 1111 1110 1011 0101
i.e. (1x2
-18
) + (1x2
-21
) + (1x2
-23
) etc = 0.0000045
Therefore the word value = 1011 0110 1001 0110 1111 1110 1011 0101
= B696FEB5
Consequently, for sensor 1 register 0001 = B696 and register 0002 = FEB5
Register Configuration M
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
r/w r/w r/w r/w r/w r/w r/w r/w r/w r/w r/w r/w r/w r/w r/w r/w
Unsigned integer / 10
Range = 0 to 6553.5