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FX Series Programmable Controllers | Devices in Detail 4 |
The reason this is not
The correct answer is therefore
Remember this is now a decimal representation of the original 16 bit - bit pattern. If the original pattern was
b)A hexadecimal view
Taking the same original bit pattern used in point a) and now adding a hexadecimal notation instead of the binary (base 2) notation the bit patterns new meaning becomes:
1 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 |
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8 | 4 | 2 | 1 | 8 | 4 | 2 | 1 | 8 | 4 | 2 | 1 | 8 | 4 | 2 | 1 |
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1 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 |
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Hexadecimal value = ((1 x 8) + (1 x 1)), ((1 x 8) + (1 x 4) + (1 x 2)), ((1 x 4) + (1 x 2) + (1 x 1)), ((1 x 4) + (1 x 1))
Hexadecimal value = 9E75
Two things become immediately obvious after a hexadecimal conversion. The first is that there is sign bit as hexadecimal numbers are always positive.
The second is there is an "E" appearing in the calculated data. This is actually acceptable as hexadecimal counts from 0 to 15. But as there are only ten digits (0 to 9), substitutes need to be found for the remaining base 16 numbers, i.e. 10, 11, 12, 13, 14 and 15. The first six characters from the alphabet are used as the replacement indices, e.g. A to F respectively.
As a result of base 16 counting, 4 binary bits are required to represent one base 16 or hexadecimal number. Hence, a 16 bit data word will have a 4 digit hexadecimal code. There is actually a forth interpretation for this bit sequence. This is a BCD or Binary Coded Decimal reading. The following section converts the original bit pattern into a BCD format.