View max1608 datasheet:

19-1639; Rev 0; 1/00 Octal SMBus-to-Parallel I/O Expanders General Description Features The MAX1608/MAX1609 provide remote input/output (I/O) ¦ Serial-to-Parallel or Parallel-to-Serial Conversions expansion through an SMBus™ 2-wire serial interface. ¦ 8 General-Purpose Digital I/O Pins Each device has eight high-voltage open-drain outputs (withstand +28V) that double as TTL-level logic inputs, providing continuous bidirectional capabilities. The open-drain outputs tailor the ¦ SMBus 2-Wire Serial Interface MAX1608/MAX1609 for use in load-switching and other ¦ Supports SMBSUS Asynchronous Suspend level-shifting applications as well as general-purpose I/O applications. ¦ 9 Pin-Selectable Slave Addresses Two complete sets of registers allow the device and its ¦ Outputs High