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Chapter 8 Experiment Synchronization 77
8.4 TTL OUT Control
The TTL-compatible logic level output (0 to +3.3 V
DC
) from the TTL Out connector on the
AUX I/O cable can be used to monitor camera status and control external devices.
NOTE:
By default, TTL OUT is active HIGH.
The timing of the level changes depends on the output type selected on the
Hardware Setup
—> Controller/Camera
tab {
Trigger
expander}:
• Shutter {Shutter Open}
This level is at a logic high while the shutter is opening and during the programmed
exposure time. The output precisely brackets shutter-open time (exclusive of the
shutter close compensation time t
c
) and can be used to control an external shutter.
• Expose (Program’d) { Exposing }
This level is at a logic high during the programmed exposure time (i.e., the time
configured in the software.) It can be used to synchronize a pulser or timing
generator with exposure.
• Read Out { Reading Out }
It is at a logic high when CCD is being read; otherwise low.
• Acquiring
{
Acquiring
}
After a start acquisition command, this output changes state on completion of the
array cleaning cycles that precede the first exposure. Initially low, it goes high to
mark the beginning of the first exposure. In free run operation it remains high until
the system is halted. If a specific number of frames have been programmed, it
remains high until all have been taken and then returns low. The timing diagram in
Figure 8-6 assumes three frames have been programmed.
Figure 8-6: Timing Diagram: TTL OUT Control
44
11
-0
14
5_
00
40
S
HUTTER
{S
HUTTER
O
PEN
}
E
XPOSE
(P
ROGRAM
’
D
)
{E
XPOSING
}
R
EAD
O
UT
{R
EADING
O
UT
}
A
CQUIRING
R
EAD
*
O
PEN
C
LOSE
E
XPOSE
1 E
XPOSE
2 E
XPOSE
3
* D
ATA
T
RANSFERRED
t
o
t
c
t
R
R
EAD
* R
EAD
*
O
PEN
O
PEN
C
LOSE
C
LOSE
t
exp