Datasheet

LP
Priority
HPD_A
0
1
0
1
0
1
HPD_B
0
1
HPD_OUT
0
1
Channel A
Z
0
1
ChannelB
0
1
HI-Z
HI-Z
LP
Priority
HPD_A
0
1
0
1
0
1
HPD_B
0
1
HPD_OUT
0
1
Channel A
Z
0
1
ChannelB
0
1
HI-Z
HI-Z
DATA
SN75DP122A
SLLS939 – NOVEMBER 2008 ............................................................................................................................................................................................ www.ti.com
Figure 37.
– Case two: In this case both HPD inputs are initially LOW and the low power pin is HIGH. In this initial
state the device is in a low power mode. Once one of the HPD inputs goes to a HIGH state, the device
comes out of the low power mode and enters active mode enabling the main link and auxiliary I/O. The
port associated with the HPD input that went HIGH is selected and the HPD output to the source is
enabled and follows the logic state of the input HPD (see Figure 38 ). This is specified as t
Z(HPD)
. Again,
the state of the Priority pin has no effect in this scenario as only one HPD input port is active.
Figure 38.
2. HPD Changes on the selected port. There are also two possible starting cases for this scenario:
– Case one: In this case only one HPD input is initially HIGH. The HPD output logic state follows the state
of the HPD input. If the HPD input pulses LOW, as may be the case if the Sink device is requesting an
interrupt, the HPD output to the source also pulses LOW for the same duration of time with a slight delay
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