CG Drives & Automation, 01-5326-01r5 Serial communication 73
9.6 Description of the EInt
formats
Eint is only used with Modbus-RTU and Modbus-TCP
protocols.
A parameter with Eint format can be represented in two
different formats (F). Either as a 15 bit unsigned integer
format (F= 0) or a Emotron floating point format (F=1).
The most significant bit (B15) indicates the format used.
See detailed description below.
All parameters written to a register may be rounded to the
number of significant digits used in the internal system.
The matrix below describes the contents of the 16-bit word
for the two different EInt formats:
If the format bit (B15) is 0, then all bits may be treated as a
standard unsigned integer (UInt)
If the format bit is 1, then is the number interpreted as this:
Value = M * 10^E, where M=m10..m0 represents a
two- complement signed mantissa and E= e3..e0 represents a
two- complement signed exponent.
Example, resolution
If you write the value 1004 to a register and this register has
3 significant digits, it will be stored as 1000.
In the Emotron floating point format (F=1), one 16-bit
word is used to represent large (or very small numbers) with
3 significant digits.
If data is read or written as a fixed point (i.e. no decimals)
number between 0-32767, the 15 bit Unsigned integer
format (F=0) may be used.
Detailed description of Emotron floating point
format
A signed number should be represented as a two
complement binary number, like below:
Value Binary
The value represented by the Emotron floating point format
is m·10e.
To convert a value from the Emotron floating point format
to a floating point value, use the formula above.
To convert a floating point value to the Emotron floating
point format, see the C-code example below.
Example, floating point format
The number 1.23 would be represented by this in Emotron
floating point format,
The value is then 123x10
-2
= 1.23
Example 15bit unsigned int format
The value 72.0 can be represented as the fixed point number
72. It is within the range 0-32767, which means that the
15-bit fixed point format may be used.
The value will then be represented as:
Where bit 15 indicates that we are using the fixed point
format (F=0).
NOTE: Parameters with EInt format may return values
both as 15 bit unsigned int (F=0) or in Emotron
floating point (F=1).
e3-e0 4-bit signed exponent. Gives a value
range:
-8..+7 (binary 1000 .. 0111)
m10-m0 11-bit signed mantissa.Gives a value
range:
-1024..+1023 (binary
10000000000..01111111111)
B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
F=1 e3 e2 e1 e0 m10 m9 m8 m7 m6 m5 m4 m3 m2 m1 m0
F=0 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
-8 1000
-7 1001
..
-2 1110
-1 1111
0 0000
1 0001
2 0010
..
6 0110
7 0111
F EEEE MMMMMMMMMMM
1 1110 00001111011
F=1 -> floating point format used
E=-2
M=123
B15 B14 B13 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0
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