Using Variables and Traces
Formatting Trace-Data Output
TDF M formats data as ASCII, integer values in measurement units. (Thus, the AUNITS command has no aect on returned data.) A line feed (ASCII code
10)follows data output. The end-or-identify state (EOI) is sent with line feed. The TDF M format is faster than the TDF P format, but requires conversion to parameter units.
TDF B formats data in measurement units as binary numbers. Numbers are transmitted usually as words. (A word is two 8-bit bytes.) The results are transmitted in the following order:
The most signicant byte is sent rst.
The least signicant byte is sent next.
EOI is sent with the last byte.
For speed at the cost of accuracy, the measurement-data-size command (MDS) may be used to consolidate the information contained in a word into one byte (MDS B). However, since trace math operations often produce numbers too large to be contained in one byte, the use of bytes instead of words as the data size is not recommended, especially during trace-math operations. Instrument preset (IP) selects words as the default data size.
TDF A and TDF I format data into absolute and indenite block-data elds. Both formats return the same kind of data, binary words (MDS W) or bytes (MDS B) as a block of data. However, the formats dier in the way they indicate the number of bytes or words returned. The TDF A format precedes the data with # A and two bytes that specify the number of data bytes returned. On the other hand, the TDF I format precedes the data with \# I" and sends EOI (end or identify) with the last byte of data. The block-data formats are available for compliance with IEEE standards. They have the same limitations as the binary format, TDF B, when bytes are chosen as the measurement data size.
The following table shows an HP-IB transmission sequence for each format. Each one transmits the +10 dBm amplitude level of a trace element. Remember that even though the analyzer transmits binary or ASCII-decimal information on HP-IB, a decimal number is always returned to the HP 9000 series 200 or 300 controller. The parenthetical numbers in the table are decimal values representing binary, 8-bit numbers.
