HP 5004A, Operating And Service Manual

Page: 64 / 74

EXPLANATION
NO CHANGE STATE
START SIGNAL
STOP SIGNAL
GATE CONTROL
FLIP-FLOPS STATES
Figure 8-4. Control State Diagram
8-86. Pseudo-Random Word Generator (Data Signal Path Continued)
8-87. The pseudo-random word generator is the central principle of the signature analysis
method.
A
shift register with some outputs fed back
is
used to generate a pseudo-random word
(signature) output. Input data goes through U6 to shift register U21. From the data
goes to and 2) input. One output from U21 (pin 12) and three outputs from U24 (pins
and 13) are fed back to the U6 inputs to combine with the input data and modify the resultant
output of the shift registers. The outputs of the two shift registers (U24 and U21) are the unique
signatures."