7.3 Quasi-bidirectional I/Os (see Fig.14)
A quasi-bidirectional I/O can be used as an input or output
without the use of a control signal for data direction.
At power-on the I/Os are HIGH. In this mode only a current
source to VDD is active. An additional strong pull-up to VDD
allows fast rising edges into heavily loaded outputs. These
devices turn on when an output is written HIGH, and are
switched off by the negative edge of SCL. The I/Os should
be HIGH before being used as inputs.