HP E1340A, User Manual

Page: 113 / 295

Using Definite Length Blocks to Transfer Data
The AFG can receive DAC codes as Definite Length Arbitrary Block Data
consisting of 16-bit integers. This is a much faster method to transfer data
than using a comma ( , ) separated list that was used in “Using DAC Data to
Generate Waveforms” on page 109. Be sure to set the upper 4 bits of the
integers to 0.
Definite Length
Block Data Format
A typical data block using the definite length format consists of:
where:
•
“ #” shows that the data to be sent is in an arbitrary block format
•
“ <non-zero digit>” is a single digit number that shows the number
of digits contained in <digits>; for example, if the <digits> value
equals 100 or 4096, the <non_zero digit> value equals 3 or 4,
respectively
•
“ <digits>” shows the number of data bytes to be sent; for example,
if 4096 data bytes are to be sent, <digits> equals 4096 (see “ Data
Byte Size” below)
•
“ <8-bit data bytes>” is the data (i.e., DAC codes) sent to the AFG
•
A typical example of a data block sending 8192 8-bit data bytes is:
#48192<data bytes>
Data Byte Size
The DAC codes are transferred to the AFG as 16-bit integer values that
meet the coding set by the IEEE 488.2 standard. Since IEEE 488.2 requires
an 8-bit code, the 16-bit integer must be sent as 2 8-bit values for each
16-bit integer. Note that the AFG requires that the most significant bit of
each 16-bit integer be sent first.
For example, to send a waveform segment consisting of 4096 DAC codes
(4096 points), the actual number of “ digits” and “ 8-bit data bytes” equals:
4096 * 2 = 8192.
# <non-zero digit> <digits> <8-bit data bytes>
Start of Data Block Data Bytes
Number of Digits in “ digits” Number of Bytes in Data
113 HP E1340A High Speed Operation Chapter 6