Trigger modes and appendant registers | External TTL trigger |
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As the trigger connector is used as an input, you can decide whether the input is 50 Ohm terminated or not. If you enable the termination, please make sure, that your trigger source is capable to deliver the desired current. If termination is disabled, the input is at high impedance.
Register | Value | Direction | Description |
SPC_TRIGGER50OHM | 40110 | r/w | Sets the 50 Ohm termination, if the trigger connector is used as an input for external trigger signals. |
The following short example shows how to set up the board for external positive edge TTL trigger. The trigger input is 50 Ohm terminated. The different modes for external TTL trigger are to be detailed described in the next few passages.
SpcSetParam (hDrv, SPC_TRIGGERMODE , TM_TTLPOS); // External positive TTL edge trigger
SpcSetParam (hDrv, SPC_TRIGGER50OHM, 1 ); // and the 50 Ohm termination of the trigger input are used
Edge triggers
Positive TTL trigger
This mode is for detecting the rising edges of an external TTL si- gnal. The board will trigger on the first rising edge that is detec- ted after starting the board. The next triggerevent will then be detected, if the actual recording/replay has finished and the board is armed and waiting for a trigger again.
Register | Value | Direction | Description | |
SPC_TRIGGERMODE | 40000 | r/w | Sets the triggermode for the board | |
| TM_TTLPOS | 20000 | Sets the trigger mode for external TTL trigger to detect positive edges | |
Example on how to set up the board for positive TTL trigger:
SpcSetParam (hDrv, SPC_TRIGGERMODE, TM_TTLPOS); // Setting up external TTL trigger to detect positive edges
Negative TTL trigger
This mode is for detecting the falling edges of an external TTL si- gnal. The board will trigger on the first falling edge that is detec- ted after starting the board. The next triggerevent will then be detected, if the actual recording/replay has finished and the board is armed and waiting for a trigger again.
Register | Value | Direction | Description | |
SPC_TRIGGERMODE | 40000 | r/w | Sets the triggermode for the board. | |
| TM_TTLNEG | 20010 | Sets the trigger mode for external TTL trigger to detect negative edges. | |
(c) Spectrum GmbH | 59 |
