70 PI-MAX/PI-MAX2 System Manual Version 5.F
drawback is that a data overrun may occur if the number of images collected exceeds the
amount of allocated RAM or if the computer cannot keep up with the data rate.
Safe Mode operation is primarily useful for experiment setup, including alignment and
focusing, when it is necessary to have the most current image displayed on the screen. It
is also useful when data collection must be coordinated with external devices such as
external shutters and filter wheels. As seen in Figure 25, in Safe Mode operation, the
computer controls when each frame is taken. After each frame is received, the detector
sends the Stop Acquisition command to the detector, instructing it to stop acquisition.
Once that frame is completely processed and displayed, another Start Acquisition
command is sent from the computer to the detector, allowing it to take the next frame.
Display is therefore, at most, only one frame behind the actual data collection.
One disadvantage of the Safe mode is that events may be missed during the experiment,
since the ST-133 is disabled for a short time after each frame.
Delay Time
Allows a delay to be inserted between successive frame acquisitions. This parameter is only
active in Safe Mode operation, in which each frame must be completely processed before the
next one can be taken. The Delay Time inserts an additional delay after the computer has
finished processing the previous frame before the next one can be acquired.
Wait for TTL and TTL Line
When checked, acquisition will not begin until a TTL high (Level 1) is detected on the
specified line of the ST-133's TTL In/Out connector. For example, suppose Wait for
TTL and TTL Line 2 were selected, and you then clicked on Focus or Acquire. Data
collection would not begin until additionally, a TTL high was detected on TTL Line 2 of
the controller’s TTL In/Out connector. Note that data acquisition, once initiated, cannot
be halted by reversing the TTL state on the selected line.
With Wait for TTL selected in Ext. Sync. mode operation, after detecting a TTL 1 on
the specified line, the system still waits for the External Sync edge before data acquisition
is initiated.
Notes:
1. TTL In/Out control is not currently supported under USB 2.0.
2. TTL control is further described in Chapter 13, starting on page 149.
Edge Trigger
When running in Ext. Sync. mode, this parameter setting determines whether
synchronization will take place on the positive-going or negative-going edge of the
External Sync signal.
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