Sierra Video 507144-00 User 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