Methods and apparatus relate to a bidirectional differential interface having a voltage-mode transmit driver architecture formed of multiple selectively enabled slices for coarse output resistance impedance matching. In an illustrative example, the transmit driver may include a programmable resistance for fine-tuning to impedance match the output resistance for transmit operation. During receive operation, protective voltage may be proactively applied to gates of drive transistors, for example, to minimize voltage stresses applied by external signal sources. Some implementations may automatically float the sources of the drive transistors, for example, to prevent back-feeding externally driven signal currents during receive mode operations. The transmit driver may have programmable voltage swing on, for example, the upper and/or lower bounds to enhance compatibility. A programmable common mode voltage node may be selectively applied, for example, through common mode resistors for receive mode operations. Various embodiments may reduce pin count for high speed bidirectional I/O.