Spectrum M2p.59 Series, Руководство по оборудованию, Страница: 107 / 190

Trigger modes and appendant registers Main analog external trigger (Ext0)
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Pulsewidth trigger for short negative pulses
The analog input is continuously sampled with the selected
sample rate. If the programmed trigger level is crossed by
the channel’s signal from higher to lower values (falling
edge) the pulsewidth counter is started. If the pulsewidth
counter reaches the programmed amount of samples, no
trigger will be detected.
If the signal does cross the trigger level again within the the
programmed pulsewidth time, a triggerevent will be detect -
ed.
To find out what maximum pulsewidth (in samples) is available, please read out the register shown in the table below:
The following example shows, how to setup the card for using pulse width trigger on EXT0 trigger input:
Register Value Direction set to Value
SPC_TRIG_EXT0_MODE 40510 read/write SPC_TM_NEG | SPC_TM_PW_SMALLER 02000002h
SPC_TRIG_EXT0_LEVEL0 42320 read/write Set it to the desired trigger level in mV mV
SPC_TRIG_EXT0_PULSEWIDTH 44210 read/write Sets the pulsewidth in samples. Values from 2 to [4G -1] are allowed. 2 to [4G -1]
Register Value Direction Description
SPC_TRIG_EXT_AVAILPULSEWIDTH 44201 read Contains the maximum possible value for the external trigger pulsewidth counter. Valid for all of the
external trigger sources.
// Setting up external X0 TTL trigger to detect low pulses that are below 1500 mV longer than 50 samples ...
spcm_dwSetParam_i32 (hDrv,SPC_TRIG_EXT0_LEVEL0, 1500);
spcm_dwSetParam_i32 (hDrv,SPC_TRIG_EXT0_MODE, SPC_TM_NEG | SPC_TM_PW_GREATER);
spcm_dwSetParam_i64 (hDrv, SPC_TRIG_EXT1_PULSEWIDTH , 50);
spcm_dwSetParam_i32 (hDrv, SPC_TRIG_ORMASK, SPC_TMASK_EXT1); // ... and enable it in OR mask