Sierra Video 507144-00 - Manual (Page 9)

Digital Mixer User’s Guide 9
point on the video output signal. The module has an intrinsic reference-to-output delay limit of one frame
time, which is 900,900 clocks in 525 line formats and 1,080,000 clocks in 625 line formats, so entering
delays greater than these values will(depending on the reference applied to the module), be limited to the
appropriate number of clocks in a full frame. Note that each delay is available with only one setting
which means that, since zero delay is available, the highest valid values are equal to the number of clocks
in a frame period MINUS ONE (900,899 for 525; 1,079,999 for 625). Otherwise, the switch values for
the desired time delay can be calculated from an absolute time goal by
1) Multiplying the desired delay time by 27,000,000,
2) rounding to the nearest whole number, and
3) expressing the result as a hexadecimal number.
This last step is most easily realized with a calculator featuring a hexadecimal number notation mode.
The resulting number is then entered into the module starting with the most significant nibble (SWA set
to position 5), even if the value of this nibble is zero. Note that this most significant nibble only has two
values; 0 or 1. Any other value will be truncated to 1. If two adjacent nibbles require the same value to
be entered , it is necessary to move SWB to another position and back again; otherwise, the module will
think you don’t want to change that register to something other than it’s original value.
When using the module to ‘fine tune’ signal re-entry timings, it is often easier to monitor the time skewed
output relative to some ’correctly’ timed signal and adjust the time delay nibbles until a satisfactory timing
is achieved. Reference-to-output delay settings beyond the maximum values allowed are automatically
limited to the maximum value available.
The following table gives a few popular values for delay settings expressed in the hexadecimal notation
used by the rear panel switches. Note that ‘second’ value time delays are actually the nearest number of
whole frames(at the line rate referred to) to the given number of seconds; allowing the video output to be
‘in time’ with the video input. The most significant digit in the ‘Switch Settings in Hexadecimal’ column
would be entered while SWA is set to position 5, the second most significant digit entered with SWA set
to position 4, etc.
Table 5: A Collection of Popular Delays and Their Corresponding Switch Settings
Reference to Output Number of Switch Settings
Delay Clock Cycles in Hexadecimal
(1) ‘525’ line
1,716 0006B4
(2) ‘525’ lines 3,432 000D68
(3) ‘525’ lines 5,148 00141C
(4) ‘525’ lines 6,864 001AD0
(5) ‘525’ lines 8,580 002184
(6) ‘525’ lines 10,296 002838
(7) ‘525’ lines 12,012 002EEC
(8) ‘525’ lines 13,728 0035A0
(9) ‘525’ lines 15,444 003C54
(10) ‘525’ lines 17,160 004308
(1) ‘625’ line 1,728 0006C0
(2) ‘625’ lines 3,456 000D80
(3) ‘625’ lines 5,184 001440
(4) ‘625’ lines 6,912 001B00
(5) ‘625’ lines 8,640 0021C0
(6) ‘625’ lines 10,368 002880
(7) ‘625’ lines 12,096 002F40
(8) ‘625’ lines 13,824 003600
(9) ‘625’ lines 15,552 003CC0