UG-707
ADV8005 Hardware Reference Manual
Some registers cannot be written to when the signal on the HPD_TXx input pin is low. When the level on the HPD_TX1 pin goes from high to
low, some registers will be reset to their default value.
The best method to determine when the level of the signal on the HPD_TXx pin is high is to use the interrupt system. An interrupt can be
enabled to notify level change on the HPD_TXx pin (refer to section 8 for more details regarding the
interrupts).
status bit which can be used to detect the presence of TMDS clock terminations from the sink. If
detects a voltage level higher than 1.8 V on the clock lines of its TMDS output port,
rx_sense_int
is set to 1.
The detection of TMDS clock terminations from downstream sink devices is useful to delay powering up the transmitter sections until the
downstream sink devices are actually ready to receive signals. A typical implementation for a sink is to tie the transmitter 5 V power signal to
HPD through a series resistor. In this case, the
will detect a high level on HPD_TX1 (HPD_TX2 for HDMI Tx 2) regardless of whether
or not the downstream sink is powered on and ready to receive a TMDS stream. For this reason, it is best to wait for both the
and
to be high before powering up the Tx core when trying to achieve minimum power consumption.
system_pd
, TX2 Main Map,
Address 0xF441[6]
This bit is used to power down the TX.
Function
system_pd
Description
0
Normal operation
1 (default)
Power down TX
hpd_state
, TX2 Main Map,
Address 0xF442[6] (Read Only)
This bit is used to readback the state of the hot plug detect.
Function
hpd_state
Description
0 (default)
Hot Plug Detect inactive (low)
1
Hot Plug active (high)
hpd_override[1:0]
, TX2 Main Map,
Address 0xF49F[5:4]
This signal is used to select the source of the internal HPD signal.
Function
hpd_override[1:0]
Description
00 (default)
HPD from HPD pin and CDC HPD
01
HPD from CDC HPD
10
HPD from HPD pin
11
HPD set to 1
rx_sense_state
, TX2 Main Map,
Address 0xF442[5] (Read Only)
This bit is used to readback the state of the Rx sense.
Function
rx_sense_state
Description
0 (default)
HDMI clock termination not detected
1
HDMI clock termination detected
rx_sense_pd
, TX2 Main Map,
Address 0xF4E6[5]
This bit is used to enable the termination sense power down.
Function
rx_sense_pd
Description
0 (default)
Termination Sense Monitoring Enabled
1
Termination Sense Monitoring Disabled
Note
should not be applied during the configuration of the HDMI Tx as it disables an oscillator required to complete the
configuration of the TMDS output clock channel. It is recommended to use
when the HDMI Tx has been completely configured.
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