smart-e 4K-RX9000, User Manual

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4K-9000 USER MANUAL V1.1
© 2018 Smart-e (UK) Ltd www.smart-e.co.uk PAGE | 38
16 HOT PLUG DETECT
Within the HDMI specification is the hot plug detect mechanism. This is the way by which a screen can tell
when it has been connected to a source. Two pins, 18 and 19, on any HDMI connecter are concerned with
this function.
Pin 18 is the +5V line, this carries a +5V signal generated by a HDMI source. This signal is used to power a
memory chip (EEPROM) within the screen it is connected to holding the EDID information (see EDID section of
this manual for further information). When the +5V signal is received by the screen it will output a +5V signal
on the hot plug detect line, this is picked up by the source and it then knows a screen is attached. A source
does not have to be outputting content for a +5V signal to be generated it simply has to be powered, even
when in standby a +5V will be generated but this does vary by device. In the same respect a screen does not
have to be turned on or set to the correct input to generate the hot plug detect signal, it is also convention to
be able to generate a hot plug detect when in standby as the received signal will usually be required to wake
the screen.
For HDBaseT to operate it must handle the hot plug detect, which it does by being able to sense the +5V line
and hot plug detect line and communicate their states between a transmit and receive device. The 4K-9000
can show at either the TX or RX end, which of the two are present or not. The below diagrams show how this
is displayed and where the problem may lay dependant on which, if any, variable is missing.