Spectrum Brands MC.31XX Edge triggers

Trigger modes and appendant registers External TTL trigger

If you choose an external trigger mode the SPC_TRIGGEROUT register will be overwritten and the trigger connector will be used as an input

anyways.

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 needed current. Please check carefully whether the source is able to fullfill

the trigger input specification given in the technical data section. If termination is disabled, the input is at high impedance.

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.

Edge triggers

Positive TTL trigger

This mode is for detecting the rising edges of an external TTL sig-

nal. The board will trigger on the first rising edge that is detected

after starting the board. The next triggerevent will then be detect-

ed, if the actual recording/replay has finished and the board is

armed and waiting for a trigger again.

Example on how to set up the board for positive TTL trigger:

Negative TTL trigger

This mode is for detecting the falling edges of an external TTL sig-

nal. The board will trigger on the first falling edge that is detected

after starting the board. The next triggerevent will then be detect-

ed, if the actual recording/replay has finished and the board is

armed and waiting for a trigger again.

SPC_TRIGGEROUT 40100 r/w Defines the data direction of the external trigger connector.

X If external triggermodes are used, this register will have no effect.

SPC_TRIGGER50OHM 40110 r/w A „1“ sets the 50 Ohm termination, if the trigger connector is used as an input for external trigger sig-

nals. A „0“ sets the 1 MOhm termination

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

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

SpcSetParam (hDrv, SPC_TRIGGERMODE, TM_TTLPOS); // Setting up external TTL trigger to detect positive edges

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.