90
M3i.48xx / M3i.48xx-exp Manual
External (analog) trigger
Trigger modes and appendant registers
External (analog) trigger
The M3i series has one main external trigger input consisting of an
input stage with programmable termination and programmable AC/
DC coupling and two comparators that can be programmed in the
range of +/- 5000 mV. Using two comparators offers a wide range
of different trigger modes that are support like edge, level, re-arm
and window trigger.
The external analog trigger can be easily combined with channel trig-
ger or with one or two of the multi purpose connectors being pro-
grammed as additional external TTL trigger inputs. The programming
of the masks and the multi purpose I/O behaviour is shown in the
chapters above.
Trigger Mode
Please find the external (analog) trigger input modes below. A detailed description of the modes follows in the next chapters..
For all external edge and level trigger modes, the OR mask must contain the corresponding input, as the following table shows:
Trigger Input Termination
The external trigger input is a high impedance input with 1 MOhm termination aginst GND. It is possible to program a 50 Ohm termination
by software to terminate fast trigger signals correctly. 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 fulfil the trigger input specification given in the technical data
section.
Please note that the signal levels will drop by 50% if using the 50 ohm termination and your source also has 50 ohm output impedance (both
terminations will then work as a 1:2 divider). In that case it will be necessary to reprogram the trigger levels to match the new signal levels.
In case of problems receiving a trigger please check the signal level of your source while connected to the terminated input.
Register
Value
Direction
Description
SPC_TRIG_EXT0_AVAILMODES
40500
read
Bitmask shoeing all available trigger modes for external 0 (Ext0) = main analog trigger input
SPC_TRIG_EXT0_MODE
40510
read/write
Defines the external trigger mode for the external MMCX connector trigger input. The trigger need to
be added to either OR or AND mask input to be activated.
SPC_TM_NONE
00000000h
Channel is not used for trigger detection. This is as with the trigger masks another possibility for disabling channels.
SPC_TM_POS
00000001h
Trigger detection for positive edges (crossing level 0 from below to above)
SPC_TM_NEG
00000002h
Trigger detection for negative edges (crossing level 0 from above to below)
SPC_TM_POS | SPC_TM_REARM
01000001h
Trigger detection for positive edges on lebel 0. Trigger is armed when crossing level 1 to avoid false trigger on noise
SPC_TM_NEG | SPC_TM_REARM
01000002h
Trigger detection for negative edges on lebel 1. Trigger is armed when crossing level 0 to avoid false trigger on noise
SPC_TM_BOTH
00000004h
Trigger detection for positive and negative edges (any crossing of level 0)
SPC_TM_HIGH
00000008h
Trigger detection for HIGH levels (signal above level 0)
SPC_TM_LOW
00000010h
Trigger detection for LOW levels (signal below level 0)
SPC_TM_WINENTER
00000020h
Window trigger for entering area between level 0 and level 1
SPC_TM_WINLEAVE
00000040h
Window trigger for leaving area between level 0 and level 1
SPC_TM_INWIN
00000080h
Window trigger for signal inside window between level 0 and level 1
SPC_TM_OUTSIDEWIN
00000100h
Window trigger for signal outside window between level 0 and level 1
Register
Value
Direction
Description
SPC_TRIG_ORMASK
40410
read/write
Defines the OR mask for the different trigger sources.
SPC_TMASK_EXT0
2h
Enable external trigger input for the OR mask
SPC_TMASK_XIO0
100h
Enable extra TTL input 0 for the OR mask. On plain cards this input is only available if the option BaseXIO is installed.
As part of the digitizerNETBOX this input is available as connector Trigger B.
SPC_TMASK_XIO1
200h
Enable extra TTL input 1 for the OR mask. These trigger inputs are only available, when option BaseXIO is installed.
Register
Value
Direction
Description
SPC_TRIG_TERM
40110
read/write
A „1“ sets the 50 Ohm termination for external trigger signals. A „0“ sets the high impedance termi-
nation
