DATA and SETup Commands
Data Preamble DescriptionData Preamble Description
The UNPacked block data is organized as 574 bytes of preamble information, followed by a variable number of bytes of data. The preamble gives information for each analyzer describing the amount and type of data captured, where the trace point occurred in the data, which pods are assigned to which analyzer, and other information.
The preamble (bytes 17 through 590) consists of the following 574 bytes:
Byte Position
174 bytes - Instrument ID (always 16500 decimal for both the HP 16554A and HP 16555A)
214 bytes - Revision Code
254 bytes - number of acquisition chips used in last acquisition
294 bytes - Analyzer ID (0 for HP 16554A, 1 for the HP 16555A/D)
The values stored in the preamble represent the captured data currently stored in this structure and not the current analyzer configuration. For example, the mode of the data (bytes 33 and 103) may be STATE with tagging, while the current setup of the analyzer is TIMING.
The next 70 bytes are for Analyzer 1 Data Information.
334 bytes - Machine data mode, one of the following decimal values: −1 = off
0 = 70 MHz (HP 16554A) or 100 MHz (HP 16555A/D) State data, no tags
1 = 70 MHz (HP 16554A) or 100 MHz (HP 16555A/D) State data with tags 2 = 70 MHz (HP 16554A) or 100 MHz (HP 16555A/D) State data with tags 3 = Fast State data, no tags (HP 16555A/D)
4 = Fast State data with tags (HP 16555A/D)
5 = Fast State data with tags (HP 16555A/D)
10 = conventional timing data on all channels
13 = conventional timing data on half channels
State data includes data acquired by State Compare and SPA machine types. There is no change in the data format.