Tabor Electronics 5251, User Manual

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4
Remote Programming Reference
Modulated Waveforms Control Commands
4-47
FM:MARKer<frequency>(?)
Description
This function programs marker frequency position. FM marker can be placed inside the following range:
(carrier frequency ± deviation frequency / 2). The marker pulse is output from the SYNC output connector.
Parameters
Name Range Type Default Description
<frequency> 10e-3 to
100e6 Numeric 1e6 Programs the marker frequency position in units of
Hz.
Response
The 5251 will return the present marker frequency value. The returned value will be in standard scientific
format (for example: 100mHz would be returned as 100e-3 – positive numbers are unsigned).
FM:DATA#<header><binary_block>
Description
This command will download FM modulating waveform data to the arbitrary FM memory. Arbitrary
modulating waveform table data is loaded to the 5251 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. Remember, downloading data to the
arbitrary FM waveform memory is very different than loading arbitrary waveform data. Waveform data
programs amplitude domain therefore, every point programs an amplitude level. On the other hand, FM
modulating waveform data programs frequency domain therefore, every point sets different sample clock
frequency.
FM:DATA#3100<binary_block>
This command causes the transfer of 10 bytes of data to the arbitrary FM waveform memory. The <header>
is interpreted this way:
•
The ASCII "#" ($23) designates the start of the binary data block.
•
"3" designates the number of digits that follow.
•
"100" is the number of bytes to follow. This number must divide by 4.
The generator accepts binary data as 32-bit integers, which are sent in five-byte words. Therefore, the total
number of bytes is always three times the number of arbitrary FM waveform points. For example, 100 bytes
are required to download 20 arbitrary FM waveform points. The IEEE-STD-488.2 definition of Definite
Length Arbitrary Block Data format is demonstrated in Figure 5-1 (refer to the TRACe subsystem). 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.
Downloading data to the arbitrary FM waveform memory is very different than loading arbitrary waveform
data. Waveform data programs amplitude domain therefore, every point programs an amplitude level. On
the other hand, FM modulating waveform data programs frequency domain therefore, every point sets
different frequency. The FM modulating waveform data is made of 32-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 32-bit words and
rearranged as five 8-bit words before it can be used by the 5251 as FM modulating waveform data. Figure