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49 Appendix D
D.4 Mode C Waveforms
Hardware-Triggered Strobe
Mode C is identical to Mode A, except that counting will not begin until a
gate edge is applied to the armed counter. The counter must be armed
before application of the triggering gate edge, while gate edges applied to
a disarmed counter are disregarded.
The counter will start counting on the first source edge after the triggering
gate edge and will continue counting until TC. At TC, the counter will
reload from the
Load register and automatically disarm itself. Counting
will then remain inhibited until a new ARM command and a new gate
edge are applied in that order.
Note that after application of a triggering gate edge, the gate input will be
disregarded for the remainder of the count cycle. This differs from Mode
B, where the gate can be modulated throughout the count cycle to stop
and start the counter.
SOURCE
WR
ARM
COMMAND
COUNT
VALUE
TC OUTPUT
TC TOGGLED
OUTPUT
GATE
X L L-1 L-2 2 1 0 L
Mode C Waveforms