32
In free-running mode the minimum frame period depends on the ROI height and the line
period. When either the frame period or exposure time setting exceeds the minimum
period, extra clocks are inserted between frames. A 32-bit frame time counter allows
frame periods from the minimum up to 64 seconds in increments of 15 nsec.
In triggered modes the frame period is also affected by the exposure delay. In multiple
trigger mode the exposure delay only affects the time until the first readout of the trigger
sequence and subsequent frames run at the free-running rate as specified. In single-
trigger mode with external exposure control, applying the trigger faster than the maximum
rate will cause the camera to skip triggers and run at a sub-multiple of the trigger
frequency. In multiple trigger mode and internal timed trigger mode, applying the trigger
faster than the maximum rate will result in the camera running at the specified free-run
rate.
Trigger pipelining is provided so that a trigger event which occurs during exposure or
readout (just during readout in external exposure mode) will generate another frame.
F
RAME
S
IGNALS TO
D
ATA
FPGA
Line Valid and Frame Valid are sent to the Data FPGA and Memory FPGA on the
fpga_ctl2 and fpga_ctl1 signals respectively. The assertion edge of Frame Valid always
leads Line Valid by at least one sysclk cycle. Frame Valid also serially transmits status
after the leading edge of Line Valid for the first line of each frame. The Data and Memory
FPGAs filter this out to create Frame Valid internally. The first status bit is valid one clock
cycle after the rising edge of Line Valid on the first line. Bit order of the status signals is:
Trigger Event (1 bit indicating external trigger since previous frame).
Frame Number (32-bit number as returned by H command) MSB first.
Frame Timestamp (32-bit number in microseconds) MSB first.
The Frame Timestamp is taken at the end of exposure, which may or may not have a
constant time relation to the time of readout. The 32-bit counter free-runs starting at 0 at
power up and wrapping every 71 minutes 35 seconds (approximately).
E
XPOSURE
M
ODES
The MV13 sensor is normally used in TrueSNAP shutter mode. The sensor has analog
frame storage and a transfer gate that allows exposure to overlap readout while exposing
all lines together. The MV40 sensor does not have analog storage and can only be
exposed in a rolling shutter mode. Thus the individual lines have different exposure
windows which may or may not overlap depending on the line rate and exposure time
settings. This is the equivalent of using the MV13 sensor with the transfer gate on all the
time.
