When only post-arm readings are specified, an error will occur when the total number of readings (ARM:COUNt * TRIGger:COUNt) is greater than 524,288 readings. However, an error will not occur if the arm count or trigger count is set to INFinity, or if the readings are going the VME bus or Local bus directly from the A/D converter.

When pre-arm readings are included in a measurement sequence with an arm count > 1, digitizer memory is segmented. When memory is segmented, the maximum number of arms is 128 and the maximum number of pre-arm and post-arm readings per arm is 524,288 / (number of arms rounded up to a power of 2).

Note If the arm count is set to INFinity, use the ABORt command to return the digitizer to the idle state.

Arm Rate When the arm count is greater than one and the sample rate is derived from the digitizer’s internal oscillator, the next arm occurs 0.5 μs after the last reading in the burst. This rate will vary with other references.

Immediate Arming Once the digitizer has been placed in the wait-for-arm state with the INITiate command, the digitizer can be armed immediately with the following command, regardless of the arm source:

ARM[:STARt][:IMMediate]

ARM Synchronization Signals

ARM:IMM is also the only way to arm the digitizer when the arm source is HOLD and the digitizer is in the wait-for-arm state.

ARM:IMM decrements the arm count by 1, and any programmed delay (other than the inherent delay) is ignored.

As indicated in the block diagram of Figure 3-5, the arm signal can be "routed" to the following locations:

"Ext 1" BNC port ECLTRG trigger lines TTLTRG trigger lines

118 Understanding the HP E1429 Digitizer

Chapter 3

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HP E1429A manual ARM Synchronization Signals