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
DATA
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
www.ti.com ............................................................................................................................................................................................ SLLS939 – NOVEMBER 2008
(see Figure 39 ). The delay of this signal through the SN75DP122A is specified as t
PD(HPD)
. If the duration
of the LOW pulse is less then t
M(HPD)
, it may not be accurately repeated to the source. If the duration of
the LOW pulse exceeds t
T2(HPD)
, the device assumes that an unplug event has occurred and enters the
low power state (see Figure 40 ). Once the HPD input goes high again, the device returns to the active
state as indicated in scenario 1. The state of the Priority pin has no effect in this scenario as only one
HPD input port is active.
Figure 39.
Figure 40.
– Case two: In this case both HPD inputs are initially HIGH and the selected port has been determined by
the state of the priority pin. The HPD output logic state follows the state of the selected HPD input. If the
HPD input pulses LOW, the HPD output to the source also pulses LOW for the same duration of time,
again with a slight delay (see Figure 41 ). If the duration of the LOW pulse exceeds t
T2(HPD)
, the device
assumes that an unplug event has occurred and the other port is selected (see Figure 42 ). The case in
Copyright © 2008, Texas Instruments Incorporated Submit Documentation Feedback 27
Product Folder Link(s): SN75DP122A