AnsweredAssumed Answered

Disabling ADV7842 Free-run

Question asked by DRC on Oct 14, 2011
Latest reply on Oct 21, 2011 by DRC

Hi, I want to disable the output free-run if no input is detected.  That is, I want the ADV7842 to not output anything.


My ADV7842 output is captured by an FPGA which measures the ADV7842's output format.


I have 3 scenarios:


HDMI Input

  • This goes through the CP.  I set [CPMap][0xBA][HDMI_FRUN_EN] = 0 and this appears to work.  When I disconnect my HDMI cable, the ADV7842 output is completely invalid.  So no problem here.


Analog-RGB Input

  • This goes through the CP as well.  The HW Manual, Section 10.13 ("CP Free-Run"), says that "The free run feature is configured automatically for analog modes."  I looked carefully and I don't see a register that disables free-run in this case.  When I disconnect my analog input cable, the ADV7842 continues to output the same format (blue field).  I want to kill the output completely.


CVBS Input

  • This goes through the SDP.  There is a register to disable free-run but it doesn't seem to work as described.  When I set [SDPMap][0xDD][SDP_FREE_RUN_AUTO] = 0, the ADV7842 simply outputs a black field instead of blue.  But it still outputs a valid NTSC output with proper timing.  I want to disable it completely.


Let me know what you think, thanks!