PI3V724 Datasheet, PDF (4/14 Pages) Pericom Semiconductor Corporation – 1 to 2 VGA Demux

PI3V724
1 to 2 VGA Demux
Truth Table
MS (Internal Switching
CE/
pull-down) Mode
Pin 30 Role SEL
0
0
Automatic
Switching
Priority Pin N/A
0
0
Automatic
Switching
Priority Pin N/A
0
1
Manual Switch-
ing
SELpin
0
0
1
Manual Switch-
ing
SELpin
1
1
x
N/A
N/A
x
Priority
0
1
N/A
N/A
x
Result
Port1 has priority
Port 2 has priority
Port 1 is active
Port 2 is active
all I/O's hi-z
Automatic switching scheme
As external monitors are properly detected, the PI3V724 can support automatic switching.
If only one monitor is connected, then the port is easily chosen regardless of what pin 30 (priority) pin status is.
Port selection (only one monitor is present)
At power on, MS pin (pin 31) is checked to determine if auto switching is enabled or not (to enable, MS needs to be LOW). Next the
part will look to see if external monitors are connected or not. If only one monitor is connected, the PI3V724 will automatically en-
able the signal path to drive the connected the monitor. OUT pin will then be pulled LOW.
Port selection (both monitors are present)
At power on, MS pin (pin 31) is checked to determine if auto switching is enabled or not (to enable, MS needs to be LOW). Next the
part will look to see if external monitors are connected or not. If only both monitors are connected, the PI3V724 will then check
the priority pin (pin 30). If pin 30 is LOW, then port 1 will have priority and therefore will be activated. However, if pin 30 is HIGH,
then port 2 will have priority and therefore port 2 will be enabled.
State Machine Reset Procedure
•
If the monitor from chosen port is disconnected, the state machine is reset (to determine chosen port, see above).
•
If MS pin status changes, state machine is reset
•
If CE/ pin goes high then low again, state machine is reset
•
If Vdd goes low and then high again, state machine resets
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www.pericom.com 10/22/14