Agilent Technologies Infiniium 90000 Q-Series, Programmer'S Manual

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Waveform Commands
34
Agilent Infiniium 90000 Series Oscilloscopes Programmer's Reference 959
This process continues until all 256 digital codes are calibrated. The
calibration process removes most of the non- linearity error of the ADC
which yields more accurate vertical voltage values.
During normal operation of the oscilloscope, the output of the ADC is
used as an address to the Calibration Look- up Table which produces
16- bit data for the oscilloscope to process and display. The output of the
ADC is a signed 8- bit integer and the output of the Calibration Look- up
Table is a signed 16- bit integer. If the amplitude of the input waveform is
larger than the maximum dc reference level of the ADC, the ADC will
output the maximum 8- bit value that it can (255). This condition is called
ADC clipping. When the 255 digital code is applied to the Calibration
Look- up Table, a 16- bit value, such as 26,188 could be produced which
represents an ADC clipped value. This number will vary from one
oscilloscope to the next.
WORD and BYTE
Data Formats
When downloading the waveform data in WORD format, the 16- bit signed
integer value for each data point is sent in two consecutive 8- bit bytes
over the remote interface. Whether the least significant byte (LSB) or the
most significant byte (MSB) is sent first depends on the byte order
determined by the BYTeorder command.
Before downloading the waveform data in BYTE format, each 16- bit signed
integer is converted into an 8- bit signed integer. Because there are more
possible 16- bit integers than there are 8- bit integers, a range of 16- bit
integers is converted into single 8- bit numbers. For example, the following
16- bit numbers are all converted into one 8- bit number.
Figure 10 Data Flow in Infiniium
D
0
D
1
D
2
D
3
D
4
D
5
D
6
D
7
Calibration
Digital
to
Analog
Converter
CPU
Aux Out
Channel In
Analog
to
Digital
Converter
Calibration
Look-up
Table
16 bits
16 bits
16 bits
8 bits
ASCII
Format
WORD
Format
BYTE
Format
Stream of
8 bit
Characters