Fluke DDS Function Generator 271 User Manual Download Page 66

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271

Users Manual

10-2

Staircase

Staircase, or multilevel square waves, are selected by pressing the

STAIR

key; when

STAIR

is selected the lamp beside the key lights. The default staircase is a 4-level

waveform with level changes at 90 ° intervals; to modify or define a new staircase select
the staircase edit menu by pressing the

EDIT

key followed by

STAIR

. When staircase

edit is selected the lamp beside the

STAIR

key flashes to show edit mode; selecting edit

mode always sets staircase on and symmetry to 50 % to permit visual checking of the
waveform.

VALS=ABS AUTO=YES
STEP=00 ACTIVE
LENGTH=0256
LEVEL=+511

The staircase edit menu is shown above. Up to 16 steps can be defined, numbered 00 to
15, with a length and level specified either in absolute terms or as a percentage of full
scale height and cycle length. When the value is set to

ABS

olute in the

VALS

field the

LENGTH

field will accept numbers in the range 0000 to 1024 (the cycle sample length)

and the

LEVEL

field will accept values in the range -512 to +511, i.e. 10-bit resolution

peak-to-peak; -512 and +511 correspond to -10 V and +10 V peaks respectively with the
amplitude on the main menu set to maximum. Note, however, that the actual peak-peak
voltage will be determined by the actual amplitude setting. When the value is set to

%MAX

in the

VALS

field both the length and level fields will accept numbers in the

range 0 to 100 % in 1 % steps.

To edit the staircase, or create a new one, proceed as follows:

Move the cursor to the

STEP

field and use the keyboard or rotary control to select the

first step to be changed; note that the level of the selected step is rapidly dithered during
editing (by an amount equivalent to the least significant bit) to help identify the correct
step on an oscilloscope. Move the cursor to the

LENGTH

field and use the keyboard or

rotary control to enter the new length for that step in the appropriate units; press

ENTER

to enter the value. If the

AUTO

field has been left set at

YES

(the default value) the

cursor will automatically move to the

LEVEL

field; enter a value in the appropriate

units and press

ENTER

again. The cursor will move back to the

LENGTH

field and the

STEP

field will be incremented by 1 ready for the next entry. If

AUTO

has been set to

, the stepping between

LENGTH

and

LEVEL

and the incrementing of the

STEP

must be done manually.

The staircase waveform is made up from steps 00, 01, 02 ... etc., in numeric order, up to
the step whose length brings the total to 1024 or more samples; all these steps, including
any in the sequence that have zero length, will be flagged as

ACTIVE

beside their step

number in the display because changing the

LENGTH

LEVEL

of any of them will

affect the waveform. Those steps beyond the last active step will be flagged

INACTIVE

even if they have a non-zero length, because changing them will not affect the waveform.
If the length of the last active step takes the total number of samples above 1024 then the
surplus samples are ignored (but the full length is displayed); if the last active sample has
insufficient samples to bring the total to 1024 then the end of the waveform is filled in
with the necessary number of samples at

LEVEL=000

Waveform editing forces the symmetry to 50 % to simplify entry; when edit mode is
ended the waveform symmetry will return to that specified on the main menu.

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