SN65C23243, SN75C23243

3V TO 5.5V DUAL RS232 PORT

SLLS513A − AUGUST 2001 − REVISED MARCH 2004

2

POST OFFICE BOX 655303

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

X

L

Normal operation with

auto-powerdown disabled

L

L

H

Yes

H

Normal operation with

H

LH

Yes

L

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

X

H

Z

Powered off while

ROUT2 is active

L

L

H

Yes

L

H

L

HH

Yes

L

L

Normal operation with

H

LH

Yes

H

H

Normal operation with

auto-powerdown

disabled/enabled

H

HH

Yes

H

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