User Manual LW120
LW120 using high-speed binary transfer in a similar way to downloading waveform data with the trace
command. High-speed binary transfer allows any 8-bit bytes (including extended ASCII code) to be
transmitted in a message. This command is particularly useful for long sequences that use a large number
of segment and sequence steps. As an example, the next command will generate two-step sequence with
12 bytes of data that contains segment number, repeats (loops) and mixed mode flag option.
SEQuence#212<binary_block>
This command causes the transfer of 12 bytes of data (2-step sequence) to the sequence table buffer. The
<header> is interpreted this way:
•
The ASCII "#" ($23) designates the start of the binary data block.
•
"2" designates the number of digits that follow.
•
"12" is the number of bytes to follow. This number must divide by 6.
The generator accepts binary data as 48-bit integers, which are sent in two-byte words. Therefore, the total
number of bytes is always six times the number of sequence steps. For example, 12 bytes are required to
download 2 sequence steps to the sequence table. The IEEE-STD-488.2 definition of Definite Length
Arbitrary Block Data format is demonstrated in Figure 4-1. The transfer of definite length arbitrary block data
must terminate with the EOI bit set. This way, carriage-return (CR – 0dH) and line feed (LF – 0aH)
characters can be used as sequence data and will not cause unexpected termination of the arbitrary block
data.
•
<binary_block>
Represents sequence table data.
The segment table data is made of 48-bit words however, the GPIB link has 8 data bas lines and accepts 8-
bit words only. Therefore, the data has to be prepared as 48-bit words and rearranged as six 8-bit words
before it can be used by the LW120 as sequence table data. Figure 4-6 shows how to prepare the 48-bit
word for the sequence step, repeat and mixed mode flag.
There are a number of points you should be aware of before you start preparing the data:
1. Each channel has its own sequence table buffer. Therefore, make sure you selected the correct active
channel (with the INST:SEL command) before you download sequence table data to the generator
2. Minimum number of sequencer steps is 1; maximum number is 4096
3. The number of bytes in a complete sequence table must divide by 6. The Model LW120 has no control
over data sent to its sequence table during data transfer. Therefore, wrong data and/or incorrect
number of bytes will cause erroneous sequence partition
4. The LSB bit is the only bit used in the mode byte. This bit has an affect on the operation of the
sequence only when Mixed Step Advance mode is active. With the LSB bit set to “0”, the sequence
generator will advance to the next step automatically. With the LSB bit set to “1”, the sequence
generator will advance to the next step only when a valid trigger signal will be sensed at the trigger
input.
Remote Programming Reference 4-51
