Nonretriggerable one-shot behavior — Evaluate: “In the 74121 (nonretriggerable), any triggers arriving before the end of the timing interval are ignored.”

Introduction / Context:
Monostable multivibrators (one-shots) generate a single pulse of predetermined width in response to a trigger. The 74121 is specifically a nonretriggerable one-shot, meaning that once the timing cycle begins, further triggers do not extend or restart the pulse until the interval completes.

Given Data / Assumptions:

• Device type: 74121 nonretriggerable monostable.
• The pulse width is determined by external R and C.
• Triggers may be negative- or positive-going depending on the selected input.

Concept / Approach:
In a nonretriggerable design, the internal gating disables the trigger path while timing is active. Therefore, new triggers are effectively ignored until the internal timing node resets, after which the device is ready for the next trigger. This prevents pulse stretching and ensures a constant pulse width independent of incoming trigger bursts.

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