Spectrum Brands MC.31XX

68 MC.31xx Manual

Channel Trigger Trigger modes and appendant registers

The following example shows, how to set up a one channel board to trigger on channel0’s rising edge. It is asumed, that the input range of

channel0 is set to the the ±200 mV range. The dezimal value for SPC_HIGHLEVEL0 corresponds then with 62.5 mV, wich is the resulting

triggerlevel.

Reading out the number of possible trigger levels

The Spectrum driver also contains a register, that holds the value of the maximum possible different trigger levels considering the above men-

tioned exclusion of the most negative possible value. This is useful, as new drivers can also be used with older hardware versions, because

you can check the trigger resolution during runtime. The register is shown in the following table:

In case of a board that uses 8 bits for trigger detection the returned value would be 255, as either the zero and 127 positive and negative

values are possible.

The resulting trigger step width in mV can easily be calculated from the returned

value. It is assumed that you know the actually selected input range.

To give you an example on how to use this formular we assume, that the

±1.0 V input range is selected and the board uses 8 bits for trigger detection.

The result would be 7.81 mV, which is the step width for your type of board withing the actually chosen input range.

Input ranges

Triggerlevel ±50 mV ±100 mV ±200 mV ±500 mV ±1 V ±2 V ±5 V ±10 V

127 +49.6 mV +99.2 mV +198.4 mV +496.1 mV +992.2 mV +1.98 V +4.96 V +9.92 V

126 +49.2 mV +98.4 mV +196.9 mV +492.2 mV +984.4 mV +1.97 V +4.92 V +9.84 V

…

64 +25.0 mV +50.0 mV +100.0 mV +250.0 mV +500.0 mV +1.00 V +2.50 V +5.00 V

…

2 +0.78 mV +1.56 mV +3.1 mV +7.8 mV +15.6 mV +31.3 mV +78.1 mV +156.3 mV

1 +0.39 mV +0.78 mV +1.5 mV +3.9 mV +7.8 mV +15.6 mV +39.1 mV +78.1 mV

0 0 V0 V0 V0 V0 V0 V0 V0 V

-1 -0.39 mV -0.78 mV -1.5 mV -3.9 mV -7.8 mV -15.6 mV -39.1 mV -78.1 mV

-2 -0.78 mV -1.56 mV -3.1 mV -7.8 mV -15.6 mV -31.3 mV -78.1 mV -156.3 mV

…

-64 -25.0 mV -50.0 mV -100.0 mV -250.0 mV -500.0 mV -1.00 V -2.50 V -5.00 V

…

-126 -49.2 mV -98.4 mV -196.9 mV -492.2 mV -984.4 mV -1.97 V -4.92 V -9.84 V

-127 -49.6 mV -99.2 mV -198.4 mV -496.1 mV -992.2 mV -1.98 V -4.96 V -9.92 V

Stepsize 0.39 mV 0.75 mV 1.5 mV 3. 9 mV 7.8 mV 15.6 mV 39.1 mV 78.1 mV

SpcSetParam (hDrv, SPC_TRIGGERMODE , TM_CHANNEL); // Enable channel trigger mode

SpcSetParam (hDrv, SPC_TRIGGERMODE0, TM_CHXPOS ); // Enable channel trigger mode

SpcSetParam (hDrv, SPC_HIGHLEVEL0 , 40 ); // Sets triggerlevel to 62.5 mV

SPC_READTRGLVLCOUNT 2500 r Contains the number of different possible trigger levels.

Trigger step width Input Rangemax Input Rangemin

–

Number of trigger levels 1+

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Trigger step width +1000 mV (-1000 mV)–

255 1+

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