Waveform Section; Events Section, Block Diagram - Fluke 9000A-006 Service Manual

9000A-006 Service

Waveform Section

The function of the waveform section is to read the probe data on a continuous basis so
that it always contains the last 640 nanoseconds of probe data in a binary form. Figure 2-6
shows that the waveform section consists of four 16-bit shift registers, each made up of
two 8-bit shift registers connected in series. (Hereafter in this description, the term shift
register refers to one of the 16-bit registers, such as that formed by U14 and U l5.) One
shift register (U14 and U15) receives VALID-Hl data from the probe and the PHASE1
signai from the GATED-OSC signal and U42. A second shift register (U40 and U4I)
receives VALID-HI data and the PHASE2 signal.
These two registers both receive high-level data samples (registers U27, U28, U55, and
U56 receive low-level data samples) but are clocked 180 degrees out of phase and 20
nanoseconds apart. The effect of this parallel, but out-of-phase, register arrangement is a
doubling of the effective operating speed. That is, the data can be clocked at double the 25
MHz speed of the registers since each register is clocked at the clock speed, but 1 80
degrees apart.
Since the two registers operate 180 degrees apart, they effectively appear as a single 32-bit
register to the incoming high data (or the incoming low data in the case of U27, U28, U55,
and U56). As a result, the two registers together always contain a binary representation of
valid high conditions at the data probe for the last 640 nanoseconds (32 times 20
nanoseconds). The other two registers (U27, U28, U55, and U56) receive valid low data
from the data probe and operate in a manner similar to that described for U14, U15, U40,
and U41 to clock in valid low probe data.
2-12
FIGURE 2-5. Events Section, Block Diagram
2-9.