Datasheet

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SLLS513A − AUGUST 2001 − REVISED MARCH 2004
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
description/ordering information (continued)
Flexible control options for power management are available when either or both serial ports are inactive. The
auto-powerdown feature functions when FORCEON is low and FORCEOFF
is high. During this mode of
operation, if the device does not sense a valid RS-232 signal, the driver outputs of its respective port are
disabled. If FORCEOFF
is set low, both drivers and receivers (except ROUT2) are shut off, and the supply
current is reduced to 1 µA. Disconnecting the serial port or turning off the peripheral drivers causes the
auto-powerdown condition to occur.
Auto-powerdown can be disabled when FORCEON and FORCEOFF
are high and should be done when driving
a serial mouse. With auto-powerdown enabled, the RS-232 port is activated automatically when a valid signal
is applied to any respective receiver input. The INV
output is used to notify the user if an RS-232 signal is present
at any receiver input. INV
is high (valid data) if any receiver input voltage is greater than 2.7 V or less than −2.7 V
or has been between −0.3 V and 0.3 V for less than 30 µs. INV
is low (invalid data) if all receiver input voltages
are between −0.3 V and 0.3 V for more than 30 µs. Refer to Figure 5 for receiver input levels.
Function Tables
EACH DRIVER
(each port)
INPUTS
OUTPUT
DIN FORCEON
FORCEOFF
VALID RIN
RS-232 LEVEL
OUTPUT
DOUT
DRIVER STATUS
X X L X Z Powered off
L H H X H
Normal operation with
H HH XL
Normal operation with
auto-powerdown disabled
L L H Yes H
Normal operation with
H LH YesL
Normal operation with
auto-powerdown enabled
L L H No Z
Powered off by
H L H No Z
Powered off by
auto-powerdown feature
H = high level, L = low level, X = irrelevant, Z = high impedance
EACH RECEIVER
(each port)
INPUTS
OUTPUTS
RIN2
RIN1,
RIN3−RIN5
FORCEOFF
VALID RIN
RS-232 LEVEL
ROUT2 ROUT
RECEIVER STATUS
L X L X L Z
Powered off while
H XL XH Z
Powered off while
ROUT2 is active
L L H Yes L H
L HH YesL L
Normal operation with
H LH YesH H
Normal operation with
auto-powerdown
disabled/enabled
H HH YesH L
auto-powerdown
disabled/enabled
Open Open H No L H
H = high level, L = low level, X = irrelevant, Z = high impedance (off), Open = input disconnected or connected
driver off