The Graphical Waveform Editor
3-66 AWG710&AWG710B Arbitrary Waveform Generator User Manual
Shift Register Generator... The Shift Register Generator... command specifies a shift regi s ter to generate
pseudo–random pulses with the value of 1 or 0 that replace the waveform data in
the edit area. The pseudo–random shift generator consists of a user–definable
register size (1 to 32 bits) and a user–specif ied nu mber of fee dba ck taps that do an
XOR operation between a specified register bit and the register output.
Figure 3-10 shows an example of the pattern generat ed for a 3–bit re giste r with an
initial value of 101 and a single tap on register bit 2.
Figure 3-10: Register value and tap setting example
The following steps describe how the instrument generates the output waveform
values.
1. Output 1 of the rightmost bit.
2. Take XOR of the output value 1 and the Bit 2 value 0 (result is 1).
3. Shift the bit values one column to the right.
4. Assign the value 1 to Bit 1, which is the XOR v alue fr om Step 2. The ne w array
of the register values is 110.
5. Repeat steps 1 to 4, with 110 as the register value.
6. Repeating output of the rightmost bit of the register and the subseque nt shift of
the register value results in the output values as shown in Figure 3-10. In this
example, the shift register output pattern starts to repeat after seven cycles.
The data generated by the shift registe r is called an M Series. If n is defined as the
number of shift register bits, then the output pattern from the shift registe r
generator (M Series length) will begin to repeat after 2n - 1 cycles.
NOTE. XOR (exclusive OR) is a boolean logic operation that outputs one if two
input values are different and outputs 0 otherwise.
1 CycleOutput
Tap