For this device, the driver and receiver are fully enabled, thus the differential outputs Y and Z follow the logic states at data input D at all times. A logic high at D causes Y to turn high and Z to turn low. In this case, the differential output voltage defined as VOD = VY – VZ is positive. When D is low, the output states reverse: Z turns high, Y becomes low, and VOD is negative. The D pin has an internal pull-up resistor to VCC, thus, when left open while the driver is enabled, output Y turns high and Z turns low.
|H||H||L||Actively drive bus high|
|L||L||H||Actively drive bus low|
|OPEN||H||L||Actively drive bus high by default|
When the differential input voltage defined as VID = VA – VB is higher than the positive input threshold, VTH+, the receiver output, R, turns high. When VID is less than the negative input threshold, VTH–, the receiver output, R, turns low. If VID is between VTH+ and VTH– the output is indeterminate. Internal biasing of the receiver inputs causes the output to go failsafe-high when the transceiver is disconnected from the bus (open-circuit), the bus lines are shorted to one another (short-circuit), or the bus is not actively driven (idle bus).
|VID = VA – VB||R|
|VTH+ < VID||H||Receive valid bus high|
|VTH- < VID < VTH+||?||Indeterminate bus state|
|VID < VTH-||L||Receive valid bus low|
|Open-circuit bus||H||Fail-safe high output|
|Short-circuit bus||H||Fail-safe high output|
|Idle (terminated) bus||H||Fail-safe high output|