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For NI 5114/5122/5124/5142/5152/5153/5154 devices, the holdoff timer is started by the Reference Trigger. When the current record finishes and the minimum number of pretrigger samples for the next record have been acquired, the holdoff timer is evaluated. If the timer has expired, the digitizer arms its Reference Trigger circuit. If the timer has not expired, the digitizer continues pretrigger sampling until the timer expires, and then arms its Reference Trigger circuit. Holdoff is applied for each Reference Trigger during a multirecord acquisition.
When the time-to-digital converter (TDC) is enabled on the digitizer, the minimum holdoff you can set is 10 µs (for the NI 5114/5122/5124/5142) or 8 µs (for the NI 5152/5153/5154). This minimum holdoff time between Reference Triggers is required for the TDC to settle; any holdoff value below these values is coerced up.
When the TDC is disabled, the minimum holdoff value you can set is decreased to 2 µs (for the NI 5114/5122/5124/5142) or 1 µs (for the NI 5152/5153/5154) when using the internal sample clock. For minimum trigger holdoff when using an external sample clock, refer to the specifications document for your digitizer.