GS4911B Datasheet, PDF (51/113 Pages) Gennum Corporation – HD/SD/Graphics Clock and Timing Generator with GENLOCK

GS4911B/GS4910B Data Sheet
If the device cannot automatically genlock the output to the applied reference, the
LOCK_LOST pin will be set HIGH and the device will operate in Free Run mode.
In this case, the user may program designated registers to manually allow locking
to occur (Section 3.6.2 on page 54).
Individual H, V, and F-locked signals can be read from the Genlock_Status register
of the host interface. Additionally, designated bits in the Genlock_Control register
may be configured to permit the genlock block to ignore invalid timing on the
HSYNC, VSYNC, or FSYNC pin when determining the locked status of the device.
These registers are described in Section 3.12.3 on page 79.
NOTE: When attempting to lock some output graphics standards to an input
reference, the device will automatically modify the output frame rate from the VESA
standard to permit cross-locking to occur. The exact change will depend on the
output standard selected and the input reference detected. Standards affected by
this behaviour are denoted by an 'a' or a 'b' suffix in Table 3-4.
VID_STD[5:0] = 62:
Setting VID_STD[5:0]=62 allows custom timing signals to be programmed in the
host register (see Section 3.10 on page 74). It has the additional feature of
disabling the validity check of the input reference signal.
The device will automatically attempt to genlock the custom output to the input
using the same process that is used when VID_STD[5:0] = 1 to 51. The user must
manually program the internal genlock block if a custom H-based timing output
signal is programmed or if a custom reference pulse is applied to HSYNC.
VID_STD[5:0] = 63:
When VID_STD[5:0]=63, the device will send the detected input reference timing
parameters to the clock synthesis and timing generator blocks. The device will
produce an output format with identical timing to the input reference. It will then lock
the output format to the reference, adjust the output timing parameters based on
the genlock timing offset registers (Section 3.2.1.1 on page 37), and set the
LOCK_LOST pin LOW.
36655 - 2 April 2006
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