Calibration Measurement; Free Run Mode; Free Run Mode Thresholds; Horizontal Free Run Conditions - Analog Devices ADV7850 Hardware Manual

Calibration Measurement

9.11.3
The input signal is accumulated during the measurement window. After the end of the window, the accumulated value is divided by the
window length and the result (average signal level over the extent of the window) is presented via the I
number format is signed with a possible range of -1024 to +1024. It is envisaged to provide the ADV7850 with a flat gray field and to
position the window in the middle of active video for a meaningful measurement.
calib[10:0], Addr 44 (CP), Address 0xE3[4:2]; Address 0xE6[7:0] (Read Only)
This readback displays the calibration value measured on the luma channel (i.e. channel A). It provides a signed value representing the
average level over the extent of the window configured by meas_ws[11:0] and meas_wl[1:0].
Function
calib[10:0]
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Note: The calibration measurement can be negative as the samples used for this measurement are taken before the offset block of the A
channel. The data is signed before the offset block and unsigned after the offset block.
9.12

FREE RUN MODE

Free run mode provides the user with a stable clock and predictable data if the input signal cannot be decoded, for example, if input video
is not present. It controls default color insertion and causes the ADV7850 to generate a default clock. The state in which this happens can
be monitored via the cp_free_run
for analog modes. The free run feature must be configured for HDMI modes.

Free Run Mode Thresholds

9.12.1
The free run threshold parameters define the horizontal and vertical conditions under which free run mode is entered. The horizontal and
vertical parameters of the incoming video signal are measured and compared with internally stored parameters, and the magnitude of the
difference decides whether or not to enter free run. The internally stored parameters are decoded by default from
vid_std[5:0]. For video standards other than the preprogrammed settings of
manually.

9.12.1.1 Horizontal Free Run Conditions

The horizontal conditions are based on the length of the incoming video line, which is measured based on the 27 MHz crystal clock. This
value is compared with the internally stored horizontal parameter, the ideal line length. ch1_f_run_th[2:0] and ch2_f_run_th[2:0] allow
the user to select the threshold for channel 1 and channel 2 respectively. The ideal line length can be manually set via the Free-run Line
Length controls, ch1_fr_ll[10:0] and ch2_fr_ll[10:0].
ch1_f_run_thr[2:0], Addr 44 (CP), Address 0xF3[2:0]
This control is used to select the free run threshold for sync channel 1. It determines the horizontal conditions under which free run
mode is entered or left. The length of the incoming video line is measured based on the crystal clock and is compared to an internally
stored parameter. The magnitude of the difference decides whether or not sync channel 1 will enter free run mode.
Rev. A May 2012
Description
Readback value
status bit. (Refer to Section 9.13 for more information.) The free run feature is configured automatically
prim_mode[3:0]
299
C register CALIB[10:0]. The
2
prim_mode[3:0]
and vid_std[5:0], the parameters can be set
ADV7850
and