User`s guide

TRIGGERING
SDK SECTION 5
Page 56
External FVB EM
IExternal FVB EM Trigger Mode is much like operating an acquisition in FVB read mode with EM gain
applied using external trigger with Keep cleans turned off. The difference surrounds the readout of the
collected data and therefore the associated readout time:
When using EM gain a second (EM) register is used to apply the gain to the acquired data, The diagram
below gives a quick overview of the readout process used in both processes.
Imagine a ‘pixel’ at position A.
Normally for the readout cycle to complete, this pixel will have to shift along the shift register and then along
the entire length of the EM Register to C before the next acquisition can begin.
When using FVB EM Trigger Mode however, the EM Register Is used as a temporary storage area and so
the pixel at A no longer needs to travel all the way to C but can stop at position B as this leaves sufficient
space in the shift register for the next acquisition; the data is in effect ‘pipelined’.
Note that not all systems support External FVB EM Trigger mode. To check if this enhanced feature is
available with your system, use the function GetCapabilities and check the ulFeature variable for bit 10
(AC_FEATURES_KEEPCLEANCONTROL) being set.