HP 16550A User Reference page 48

Timing acquisition
mode field
The Format Menu
Timing Acquisition Mode Field (Timing only)
~
( Run
{symbols)
~CEO
________ uuuu
15 ... 67 . '. 0
Transi l1onal Full Channel 125 MHz
I L _ _ J - - - - - - - - - - - - - - - L _ _ _ _ J
I
*******=fl********
I
Transitional Half Channel 250 MHz
Half Channel 125 MHz
~--------+----
Acquisition mode
selection menu
Lab6
Lab7
Lab6
Timing Acquisition Mode Selection
Transitional Full Channel 125 MHz Mode
The total memory depth is 4 Kbytes per charmel with a channel width of 34
charmels per pod pair. Data is sampled for new transitions every 8 ns.
When the Timing analyzer runs in the 125 MHz mode, it operates very similar
to the state analyzer with count Time turned on. The only exceptions are
that the store qualification comes from transition detectors instead of the
sequencer. Also, the analyzer uses an internal clock.
With 4 Kbytes of memory per channel and count Time turned on, the
analyzer uses half its memory (2 Kbytes) to store time tags. It should be
noted that each pod pair must store transitions at its own rate, therefore it
must store its own set of time-tags. You do not have the option of using a
free pod to retain full memory as you have in the normal state mode.
When a transition is detected after a sample with no detected transition,
two samples are stored. One sample is a "before transition sample" and the
other is an "after transition sample." Then, as long as there are transitions in
the subsequent sample, only 1 sample is stored. When the next sample
occurs without a transition, the two stored sample sequence (one before, one
after) repeats with the next detected transition.
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