National Semiconductor LMH1983, Руководство пользователя

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LMH1983 Evaluation Kit Users Guide
Page 9 of 25
I
2
C SLAVE ADDRESS
The I
2
C address select jumper JP9 (3-way) can be configured as follows to select one of
the three I
2
C slave addresses offered by the LMH1983. The default for the board, and
for the ALP software is address ‘66h which corresponds to no jumper installed.
Table 1: LMH1983 I
2
C Slave Address Selection
7-bit I
2
C Slave Address JP1 Jumper Setting LMH1983 Address Input State
65’h (hex) Short Pins 1-2 Externally tied low
66’h Open Pins Internally biased to mid-supply
67’h Short Pins 2-3 Externally tied high
Observing the Outputs
The LMH1983 generates four clock signals (CLKout1, CLKout2, CLKout3, CLKout4)
and four timing signals (TOF1, TOF2, TOF3, TOF4). The LMH1983 outputs are
differential outputs, and can be observed directly at JP13, JP14, JP15 and JP16. There
are 100
Ω termination resistors situated near the connectors (R60,R66, R73 and R78). If
the differential signals are to be observed with a high impedance differential scope probe,
it can be attached directly to the pins. If it is desired that the differential outputs drive a
load, the load resistor should be moved to be adjacent to the final load. In addition to the
differential outputs, there are 50Ohm single ended outputs as well. These are provided
by using LMH0302 SDI cable drivers. On the initial version of the evaluation board
these outputs exhibit some undershoot and ringing at 4GHz which degrades the jitter
performance of these outputs.
Configuring the board for operation with an analog video
reference signal
The LMH1983 Evaluation board includes an LMH1981 sync separator which is able to
extract the timing signals from a broad range of analog sync signals. To use this feature,
install a jumper on JP4 (MUX ENABLE), and one on JP3 (Input Select). Supply the
reference signal to J1 (analog Ref In), and you can monitor the extracted H, V and F
signals at the yellow test points just to the left of the LMH1983.
The GUI will display what format is being detected under the PLL1
The LMH1983 can automatically detect and synchronize to the following reference input
formats received at its input pins:

HVF Sync timing from SMPTE standard video formats
o
525i/29.97/30
o
525p/59.94/60