Interpreting Returned Data - Anritsu LMR Master S412E Programming Manual

DMR 2 Commands

Interpreting Returned Data

The following section provides two conversion examples on interpreting returned data.
Examples are provided for both integer and real number formats.
Converting INTeger,32 and REAL,32 Values
The number of bytes the instrument returns is dependent on the parameter specified with the
":TRACe[:DATA]? ALL|CONStellation|HISTogram|PROFile|SPECtrum|EYEDiagram"
command on page
• The first 10 bytes make up the "header" information.
• The data portion contain tags to demarcate different data sets. The first valid datapoint
starts x bytes after the header where x is the number of characters that make up the
tag. For example, <CONSTELLATION> is 15 bytes. Skip as many bytes as there are
characters to get to the start of the data.
• Spectrum and Histogram datapoints consists of 4 bytes.
• Eye Diagram datapoints [12 X-axis points and (12 x ((551 / Number Of Symbols) - 1))
Y-axis points] are 4 bytes each.
• Each Constellation datapoint consists of 8 bytes.
• The first 4 bytes are the I component
• The next 4 bytes are the Q component.
• The returned value is in little endian format (the little end comes first).
• Negative numbers are represented in two's complement format.
• The data is scaled by a factor of 1e3.
Converting INTeger,32 Example:
The instrument returns the following Spectrum data point in INT,32 format:
b9 c0 fd ff
1. Convert from little endian to big endian:
ff fd c0 b9
2. Since the MSb in both components is 1, they are negative numbers.
3. The binary representation is:
11111111111111011100000010111001
4. Convert from two's complement (not the bits and add 1):
100011111101000111
5. Convert the binary values to decimal:
147271
6. Take out the 1e3 scale factor:
147271/1000 * -1 = -147.271
S412E PM
14-37.
PN: 10580-00319 Rev. N
14-5 :FORMat Subsystem
14-13