Racal Instruments 3155 Spezifikationen PDF herunterladen (Seite 123)

User Manual 3155

Programming Reference 4-12

Error Codes

Description

PXI_COMMAND_ERROR

if value is 0x8000000, error is in SCPI syntax or other errors relating to instrument setability .SCPI

error list is given in the SCPI Commands reference.

If value is larger than 0x8000000, look for problems in the communication with the 3155. The most

probable cause for such an error is not invoking the Arb Detector program after you power up your

computer.

Description

The 3155 is a waveform generator. There are three types of waveforms that the instrument

can generate: 1) Standard waveforms, 2) Arbitrary waveforms and 3) Waveforms that are

frequency modulated by arbitrary modulating waveforms. Every time that the instrument is

asked to generate waveforms, it must have waveform values stored in memory.

The generator has nine built-in standard waveforms shapes. There is no need to download

waveform values to the generator for it to be able to output one of these waveforms. How-

ever, every time you select one of the standard functions, the firmware computes the data

and places the waveform values in waveform memory.

Not so if you want to generates arbitrary waveforms. In this case, you have to generate the

values externally and then download the data to the generator. There are two separate

memory banks built into the instrument. The main and the largest memory bank generates

the arbitrary (USER) waveforms. This memory has vertical resolution of 14 bits and a depth

(or length) of 1 Meg. The other memory bank is used for arbitrary waveforms that modulate

the carrier frequency. This bank is completely different than the main memory bank in the

way that it stops data. Data structures for both memory types are given later in the manual.

The SendBlock() function is used for sending arbitrary blocks of data to the instrument. Here

are some simple steps for you to follow in your application. Two examples are given: Using

the SendBlock() function with resident data array and using SendCommand() with an exter-

nal data file.

Example 1

1. Use SendCommand to program Trac:sel 1

2. Use SendCommand to program Trac:def 1,1000

3. Prepare your waveform data

Call SendBlock(hInstr, 1, "", (void*)wav, 1000*2). Note that each data point requires

2 bytes.

Example 2

1. Use SendCommand to program Trac:sel 1

2. Use SendCommand to program Trac:def 1,1000

Prepare your waveform data and save in a file. Concatenate the file name with

trace#

4. Call SendCommand(0,trac#<file_name>)

Arbitrary Waveform Data Structure

The arbitrary waveform data structure is actually very simple. It contains 16-bit words in the

range of –8192 to 8291, converted to short format (Intel binary representation)

Arbitrary FM Waveform Data Structure

The arbitrary FM waveform data structure is a bit more complicated. It is made of sample

clock frequencies and not voltages as was the structure for the arbitrary waveform data.

Sample clock range is from 50 S/s to 100MS/s. The arbitrary FM waveform memory has

200K points maximum however, you can choose to use shorter waveform length by specify-

ing the “size” parameter in the SendBlock() function.

Here are some simple steps that show how to prepare the arbitrary FM waveform data.

1. Define a structure:

Struct Fmtag( int pt;

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