National Instruments NI Vision PCI-1409, User Manual, Page: 17 / 40

Chapter 2 Hardware Overview
© National Instruments Corporation 2-5 NI PXI/PCI-1409 User Manual
signals to acquire the video signals directly. You can use this mode to
acquire from a line scan camera.
• External HSYNC/VSYNC Mode —In external HSYNC/VSYNC
mode, the NI 1409 receives the external HSYNC and VSYNC from
the connector and internally generates the PCLK signal. The NI 1409
genlock circuitry locks to the external HSYNC and VSYNC signals.
You can use this mode to acquire from VGA monitors
(640
×
480 resolution).
• External HSYNC/VSYNC (HLOCK only) Mode —In external
HSYNC/VSYNC (HLOCK only) mode, the NI 1409 receives the
external HSYNC and VSYNC signals and internally generates the
PCLK signal. In this mode, the NI 1409 genlock circuitry uses only the
HSYNC signal for locking. You can use this mode to acquire from
asynchronously reset cameras that output a continuous HSYNC.
Analog Front End Considerations
The analog front end of the NI 1409 features a calibrated gain circuit,
programmable DC-restore circuit, and 10-bit ADC as shown in Figure 2-2.
Figure 2-2. NI 1409 Analog Front End
10-Bit/8-Bit Mode
The NI 1409 always digitizes the incoming video signal to 10 bits of
resolution. In 10-bit mode, the NI 1409 has four fixed, full-scale ranges for
calibrating the gain for each range. Because the nominal full-scale ranges
are 0.20, 0.35, 0.70, and 1.40 V, the gain is not continuously variable in this
mode. To maintain compatibility with other analog image acquisition
devices, the NI 1409 has an 8-bit mode that converts the 10-bit data from
the ADC to 8-bit data in the lookup table (LUT) after gain correction and
any digital filtering has occurred.
DC-restore
1 of 4
Gain
Analog
Video
10-bit
ADC
Digital Gain
Correction,
Filtering, and LUT
10- or 8-bit