Digital Electronics — 74123 Retriggerable Monostable Is there any limit to how many times a 74123 can be retriggered before its current pulse times out? Assume each new trigger arrives before the existing output pulse would have ended.

Introduction / Context:
The 74123 is a dual retriggerable monostable multivibrator. In retriggerable operation, any valid trigger that occurs while the output is still active extends the pulse. This question tests understanding of how retriggering affects pulse width and whether there is a fundamental limit on the number of retriggers.

Given Data / Assumptions:

• Device: 74123 retriggerable one shot.
• Assume trigger pulses meet input thresholds and minimum widths.
• Assume supply voltage and temperature are within datasheet limits.

Concept / Approach:
The output pulse width of a retriggerable one shot is determined by the RC timing network and an internal threshold. When another trigger arrives during the active pulse, the timing cycle restarts from that instant, effectively adding more time.

Step-by-Step Solution:
1) Initial trigger starts a pulse of width T = k * R * C (k is a device constant).2) If a new valid trigger arrives before the output returns low, the internal timing capacitor is considered as restarting the timing interval from that moment.3) Each additional in-window trigger extends the output by a further interval approximately equal to T from the latest trigger edge.4) The process can continue as long as triggers keep arriving before timeout and are valid in amplitude and width.

Verification / Alternative check:

Why Other Options Are Wrong:

• yes: Suggests a hard numeric cap, which the device doesn't impose.
• only up to 3 times: Arbitrary limit not present in device operation.
• only once per RC time constant: Contradicts retriggerable behavior which allows repeated extensions.

Common Pitfalls:
Confusing retriggerable with nonretriggerable one shots; forgetting input validity constraints; overlooking that practical limits are due to input conditioning or maximum trigger rates, not a count limit.

Final Answer:
no