User manual

Appendix D. Waveform of each mode
The PCI-1780 offers 16 powerful counter functions to fulfill your
industrial or laboratory applications. This chapter will describe each
mode in detail with the waveform diagram.
Counter mode descriptions
Counter Mode register bits CM15-CM12 and CM6-CM4 select the
operating mode for each counter (see Table D-1). To simplify references
to a particular mode, each mode is assigned a letter from A through X.
Representative waveforms for the counter modes are illustrated in
Figure A through X (because the letter suffix in the figure number is
keyed to the mode, Figures M, N, P, Q, V, W do not exist).
The figures assume counting on rising source edges. Those modes,
which automatically disarm the counter (CM4 = 0) are shown with the
WR pulse entering the required ARM command; for modes which count
repetitively (CM4 = 1) the ARM command is omitted. Both a TC output
waveform and a TC Toggled output waveform are shown for each
mode.
The symbols L and H are used to represent count values equal to the
Load and Hold register contents, respectively. The symbols K and N
represent arbitrary count values. For each mode, the required bit pattern
in the Counter Mode register is shown; "don't care" bits are marked "X".
These figures are designed to clarify the mode descriptions.
To keep the following mode descriptions concise and to the point, the
phrase "source edges" is used to refer to active-going source edges only,
not to inactive-going edges. Similarly, the phrase "gate edges" refers
only to active-going gate edges. Also, again to avoid verbosity and
euphuism, the descriptions of some modes state that a counter is stopped
or disarmed "on a TC, inhibiting further counting."
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