lm9627 National Semiconductor Corporation, lm9627 Datasheet - Page 14

• Manufacturer Part Number: lm9627
• Description: Color Cmos Image Sensor Vga 30 Fps
• Manufacturer: National Semiconductor Corporation

Functional Description
5.4
In CPU snapshot mode, the FTriggerEN is not set automatically
and an Interrupt generator can be enabled.
Hence, upon the receipt of a snapshot or
signal, the integrated timing and control circuit will generate an
internal TRIGGER signal as shown in figure 19 and then wait in
the IRQ state for the FTriggerEN bit to be manually set as shown
in figure 21.
Once the FtriggerEn bit is set the integrated timing and control
circuit will start resetting the array one row at a time. At end of
the reset cycle the timing and control circuit will signal the shut-
ter to open via extsync pin or FtSync bit. At the end of the pro-
grammed integration time the shutter will be signalled to close,
and the pixel read-out will commence as shown in figure 18a. At
the end of the read-out sequence the FTriggerEN will be auto-
matically disabled and the sensor will return to video capture
mode as shown in figure 20.
If an external shutter is not available then at least two frames
need to be taken so that the pixels can be integrated over one
frame as shown in Figure 18b.
To use CPU snapshot mode the SsEngage bit of the
SNAPSHOTMODE1 register must be set to one.
An interrupt generator can be enabled in CPU snapshot mode
by setting the SnapIntEn bit of SNAPSHOTMODE1 register. An
interrupt will be generated on the external interrupt pin, irq,
when a snapshot sequence is triggered (TRIGGER=1) or when
the array readout is complete at the end of the snapshot
sequence as shown figure 21.
Confidential
SnapShotPol
SnapEnable
snapshot
FTriggerNow
Figure 20. Auto Snapshot Mode State Diagram
Figure 19. Snapshot Trigger Generation Logic
CPU Snapshot Mode
PREVIEW
VIDEO
SNAP
c:TRIGGER==1
(continued)
a:FTriggerEn=1
a:FTriggerEn=0
FTriggerNow
TRIGGER
trigger
14
When an interrupt is generated by a TRIGGER event, the
SsTrigFlag bit in the SNAPSHOTMODE1 register is set. Simi-
larly when an interrupt is generated at the completion of a read-
out the SsRdFlag in the SNAPSHOTMODE1 register is set.
The polarity of the irq pin can be programmed. The interrupt can
only be cleared by reading SsTrigFlag and the SsRdFlag as
shown in figure 22.
5.5
The snapshot pin can be programmed to operate in pulse trig-
ger mode where one snapshot sequence is executed per active
pulse or in level trigger mode where by snapshot sequences are
repeated as long as the level on the snapshot pin is held active.
(see figures 20 and 21).
Pulse and level trigger modes can be set by programming the
SnapshotMod bit in the SNAPSHOTMODE0 register.
SsRdFlag
SnapIntEn
SsTrigFlag
Figure 21. CPU Snapshot Mode State Diagram
Figure 22. Interrupt Request Generation Logic
Pulse & Level Trigger Mode
IrqPol
PREVIEW
VIDEO
SNAP
IRQ
c:FTriggerEn==1
c:TRIGGER==1
a:SsTrigFlag=1
a: FtTriggerEn = 0
a: SsRdFlag = 1
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irq