Fundamental TechnologiesVoyager LECP Pages |
Record Format Tables Common to Cruise, Far Encounter, Near Encounter, and Cruise 5A
Explanation of Data Quality Word Contents
BITS* |
VARIABLE |
DESCRIPTION |
0-7 |
NBI |
Number of Basic Intervals-contains the number of basic accumulation intervals over which the corresponding rate is accumulated. The accumulation time in milliseconds is given by NBI*BAI. (See Table 1, ITEM 22.) |
8-10 |
MPB |
Motor Position-contains the motor position at the end of the accumulation interval. MPB ranges from 0 to 7, corresponding to the LECP sectors 1 thru 8 respectively. If MP or NMS (see Table 1 ITEMs 18 and 19) are less than zero then MPB is invalid. |
11 |
MCF |
Motor Centered Flag-is set if the status word indicates that the motor was centered within the sector. It is zero otherwise. |
12 |
MMF |
Motor Movement Flag-is set if a motor step occurred during the accumulation interval. It is zero otherwise. |
13 |
DL |
Discriminator Level-is set if the LECP Beta detector is set to its high threshold state. It is reset otherwise. |
14-15 |
SS |
Switch State-defines which of the β or β' and δ or δ' rates are accumulated. 00=not known, 01=β' - δ detectors on, 10= β - δ' detectors on, 11=mixed. |
BIT 0 is the Least Significant Bit. If all bits=0 then datum is missing.
Explanation of I*1 Representation
Bit 7 | Bit 6 | Bit 5 | Bit 4 | Bit 3 | Bit 2 | Bit 1 | Bit 0 |
MSB | LSB |
Explanation of I*2 Representation (VAX Fortran Volume 2 Language Reference Manual C-1)
Bit 15 | Bit 14 | Bit 13 | Bit 12 | Bit 11 | Bit 10 | Bit 9 | Bit 8 | Bit 7 | Bit 6 | Bit 5 | Bit 4 | Bit 3 | Bit 2 | Bit 1 | Bit 0 |
Sign | MSB | LSB |
Sign = 0(+), 1(-)
Integers are stored in a twos complement representation. INTEGER*2 values are in the range
–32768 to 32767, and are stored in two contiguous bytes aligned on an arbitrary byte boundary.
For example:
+22 | = 0016 (hex) |
-7 | = FFF9 (hex) |
R*4 Representation (VAX Fortran Volume 2 Language Reference Manual C-5 and User Manual 10.5.1.2)
Bit 15 | Bit 14 | Bit 13 | Bit 12 | Bit 11 | Bit 10 | Bit 9 | Bit 8 | Bit 7 | Bit 6 | Bit 5 | Bit 4 | Bit 3 | Bit 2 | Bit 1 | Bit 0 |
Sign |
Exponent |
Fraction |
|||||||||||||
Fraction |
|||||||||||||||
Bit 31 | Bit 30 | Bit 29 | Bit 28 | Bit 27 | Bit 26 | Bit 25 | Bit 24 | Bit 23 | Bit 22 | Bit 21 | Bit 20 | Bit 19 | Bit 18 | Bit 17 | Bit 16 |
Sign = 0(+), 1(-)
The exponent for the REAL*4 format is stored in binary excess 128 notation. Binary exponents from –127 to 127 are represented by the binary equivalents of 1 through 255. For each floating-point format, fractions are represented in sign-magnitude notation, with the binary radix point to the left of the most significant bit. Fractions are assumed to be normalized, and therefore the most significant bit is not stored (this is called “hidden bit normalization”). This bit is assumed to be 1 unless the exponent is 0. If the exponent equals 0, then the value represented is either zero, or it is a reserved operand. 0.0 is any bit pattern that has an exponent field of 0 and a sign bit of 0, regardless of the value of the fraction. REAL*4 (F_Floating) data is four contiguous bytes starting on an arbitrary byte boundary. Bits are labeled from the right, 0 through 31. The form of REAL*4 (F-floating) data is sign magnitude, with bit 15 the sign bit, bits 14:7 an excess 128 binary exponent, and bits 6:0 and 31:16 a normalized 24 bit fraction with the redundant most significant fraction bit not represented. The value of F_floating data is in the approximate range 0.29 x 10^{-38} through 1.7 x 10^{38}. The precision is approximately one part in 2^{23}; that is, typically, seven decimal digits.
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Last modified 8/1/05, Tizby Hunt-Ward
tizby@ftecs.com