SCPS144C May 2006 – May 2015 P82B96
PRODUCTION DATA.
Two or more Sx or Sy I/Os must not be connected to each other on the same node. The P82B96 design does not support this configuration. Bidirectional I2C signals do not have a direction control pin so, instead, slightly different logic low-voltage levels are used at Sx/Sy to avoid latching of this buffer. A standard I2C low applied at the Rx/Ry of a P82B96 is propagated to Sx/Sy as a buffered low with a slightly higher voltage level. If this special buffered low is applied to the Sx/Sy of another P82B96, the second P82B96 does not recognize it as a standard I2C bus low and does not propagate it to its Tx/Ty output. The Sx/Sy side of P82B96 may not be connected to similar buffers that rely on special logic thresholds for their operation.
The Sx/Sy side of the P82B96 is intended for I2C logic voltage levels of I2C master and slave devices or Tx/Rx signals of a second P82B96, if required. If Rx and Tx are connected, Sx can function as either the SDA or SCL line. Similarly, if Ry and Ty are connected, Sy can function as either the SDA or SCL line. There are no restrictions on the interconnection of the Tx/Rx and Ty/Ry I/O pins to other P82B96s, for example in a star or multi-point configuration (multiple P82B96 devices share the same Tx/Rx and Ty/Ry nodes) with the Tx/Rx and Ty/Ry I/O pins on the common bus, and the Sx/Sy side connected to the line-card slave devices.
In any design, the Sx pins of different devices should never be linked, because the resulting system would be very susceptible to induced noise and would not support all I2C operating modes.