GS4911B Datasheet, PDF (25/113 Pages) Gennum Corporation – HD/SD/Graphics Clock and Timing Generator with GENLOCK

GS4911B/GS4910B Data Sheet
1.5 Output Timing Signals
Table 1-3 describes the output timing signals available to the user via pins
TIMING_OUT_1 to TIMING_OUT_8. The user may output any of the signals listed
below on each pin by programming the Output_Select registers beginning at
address 43h of the host interface.
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Table 1-3: Output Timing Signals
Signal Name
H Sync
H Blanking
Description
Default Output Pin
The H Sync signal has a leading edge at the start of the horizontal sync pulse.
Its length is determined by the selected video standard (see Table 1-2), or
according to custom timing parameters programmed in the host interface (see
Section 3.10 on page 74).
The width of the H Sync output pulse is determined by the selected video
standard. Table 1-2 lists the H Sync width (in clocks) of each pre-programmed
video and graphics standard recognized by the GS4911B/GS4910B. Custom
video timing parameters may also be programmed in the host interface to
define a unique H Sync width (see Section 3.10 on page 74).
In Genlock mode the leading edge of the output H Sync signal is nominally
simultaneous with the half amplitude point of the reference HSYNC input. This
timing may be offset using the Genlock Offset registers beginning at address
1Bh of the host interface (see Section 3.2.1.1 on page 37).
By default, after system reset, the polarity of the H Sync signal output will be
active LOW. The polarity may be selected as active HIGH by programming the
Polarity register at address 56h of the host interface (see Section 3.12.3 on
page 79).
TIMING_OUT_1
The H Blanking signal is used to indicate the portion of the video line not
containing active video data.
TIMING_OUT_2
The H Blanking signal will be LOW (default polarity) for the portion of the video
line containing valid video samples. The signal will be LOW at the first valid
pixel of the line, and HIGH after the last valid pixel of the line.
The H Blanking signal remains HIGH throughout the horizontal blanking period.
The width of this signal will be determined by the selected video standard (see
Table 1-2), or according to custom timing parameters programmed in the host
interface (see Section 3.10 on page 74).
When in Genlock mode, the output H Blanking signal will be phase locked to the
reference HSYNC input. This timing may be offset using the Genlock Offset
registers beginning at address 1Bh of the host interface (see Section 3.2.1.1 on
page 37).
The default polarity of this signal may be inverted by programming the Polarity
register at address 56h of the host interface (see Section 3.12.3 on page 79).
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