Matrox Helios Series Installation And Hardware Reference page 58

58 Chapter 4: Matrox Helios hardware reference
Synchronization
Clock
Quadrature decoder
For each PSG, the board can supply one horizontal (HSYNC) and one vertical
(VSYNC) synchronization signal to the video source. Through the Camera Link
connectors, the board also receives synchronization data (frame valid, line valid,
and data valid) along with the video data; refer to the Camera Link specification
for a description of the synchronization data.
Note that the Camera Link standard does not regulate how to transmit an
interlaced video signal, however you can define an auxiliary signal as a field polarity
input signal and transmit the field polarity on this signal.
For each PSG, the board can supply a clock signal to the video sources. Through
each of the video input Camera Link connectors, the board can also receive a clock
signal.
Each PSG features a quadrature decoder that can decode input from a rotary
encoder with quadrature output. A rotary encoder (sometimes called a quadrature
encoder) is a device that provides information about the position of a rotating
shaft. The encoder outputs a two-bit code (also known as gray code) on two pairs
of LVDS wires in a precise sequence: 00 01 11 10. The sequence determines the
position of the rotating shaft and the direction of rotation.
The quadrature decoder can decode gray code and update a 16-bit internal
counter. You can read the counter at different stages of the grab or trigger a grab
based on the value of the counter. The quadrature decoder can support a maximum
encoder frequency equal to the pixel clock frequency for the camera.
❖ Note that an external source must be used to power the rotary encoder (for
example, the computer's 5 V power source).
For each PSG, you can program two auxiliary signals as quadrature inputs. One
to carry the first bit, and one to carry the second. Quadrature decoder settings can
be toggled using the MIL-Lite function MdigControl() with
modifying the DCF file.
, or by
M_ROTARY...