SN65LVCP40 : What is output when input is not connected?

Johnny

If you are refering to LVCP40, there is no built in fail safe mechanism for the o/p to shut off if the input is floating or there is any noise coupled from input, the o/p wil switch.

The datasheet refers to external failsafe recommendation though:

RECEIVER FAIL-SAFE RESPONSE

If the input is removed from a powered receiver of the 'LVCP40, there are no internal fail-safe provisions to
prevent noise from switching the output. Figure 25 shows one remedy using 1.6 kW resistors to pull up on one
input to the SN65LVCP40 supply, and pull down the other input to its ground. Assuming the differential noise in
the system is less than 25 mV, this maintains a valid output with no input. If the noise is greater than 25 mV,
lower fail-safe resistance is required.

If the driver is another SN65LVCP40, attenuation from the driver to receiver must be less than 250 mV or 6 dB.
This value comes from the minimum output of 500 mV into 100 W less the minimum recommended input voltage
of 100 mV, 25 mV for noise, and 125 mV for the maximum fail-safe bias.
The fail-safe bias also introduces additional eye-pattern jitter depending upon the input voltage transition time,
but is designed to be less than 10% of the unit interval.
The only other options are to have a hardware interlock that removed power to the receiver, or switched in a
fail-safe bias, or rely on error detection to ignore random inputs.