Sierra Video RTR-804 - Manual (Page 42)

SIERRA VIDEO
36
Circuit Description
Please refer to the Block Diagram and the schematic, 430004-00, when reading the
circuit description.
This board is a simple serial digital video switch that can operate with inputs from
270Mb/s to 3Gb/s. The board uses two slots in a ten slot openGear frame and 4 slots in a
20 slot openGear frame. It will switch on the correct line in the vertical interval if a color
black reference is present at one of the two reference inputs on the rear of frame. The
user must use DashBoard to select which one of the two references to use and the user
must also set the format of the reference and the format of the video that is being
switched. The reference and video formats must have the same frame rate or have frame
rates between the reference and video that have a ratio of either 1:2 or 2:1, i.e. 25Hz
frame rate reference with a video frame of 50Hz. The switch point defaults to the mid line,
50%, point and can be adjusted +/- 2 lines, 1%-99% of the line using DashBoard.
There is one assembly used for all four versions of this product.
The veresions are:
8X4
8X2
4X4
4X2
The 8X4 is the fully loaded version and uses all inputs and all four outputs. By deleting
input EQ's and Output Drivers along with their Re-clockers any of the versions can be
created. Besides the DashBoard application that controls the crosspoint routing there is
also a 3 pin mini XLR connector , RS-485, for a control and a 9 pin "D" connector, RS-
422/232, for serial control.
The block diagram is on the following page and gives a high altitude view of the functions
in the board. The block diagram as shown represents a 8X4 router. All eight inputs are
received by an auto equalizing input stage that compensates for loss in the connecting
cable. The equalization can be bypassed on an input by input baisis. This may be
necessary if the user wishes to use the router with DVB-ASI inputs. Each EQ sends a
carrier detect signal to the processor so that the user will get an indication of no input
signal in DashBoard. The output of the EQ stage is differential and sent to an 8X8
crosspoint.
Since this router has a maximum of four outputs only four outputs are used from the 8X8
crosspoint. The first four unused outputs of the crosspoint are used in a silent switch
version of this product with the last four outputs from the crosspoint used as a bypass
around the silent switch. In this product the last four crosspoint outputs are used for the
video path full time by select them at the input of the re-clockers 2 to 1 input mux. All the
no connects, NC, are connections to the unused silent switch.
The outputs from the crosspoint are differential into the re-clockers. Each re-clocker is
controlled through a SPI interface and can be used to bypass the re-clocking, set the re-
clocker to auto determine signal data rate or manually set data rate. The differential
output of the re-clocker is internally terminated in 50 ohms with the destination of the
output terminated differentially in 50 ohms.
Each output stage drives one output BNC at the rear of the frame. There is no signal
inversion from input to output. This is necessary in order to pass DVB-ASI signals.