Crystal oscillator frequencies MIDI Synchronous serial communication References Further reading Serial Port Complete: COM Ports, USB Virtual COM Ports, and Ports for Embedded Systems; 2nd Edition; Jan Axelson; Lakeview Research; 380 pages; 2007; . Serial Port Complete: Programming and Circuits for RS-232 and RS-485 Links and Networks; 1st Edition; Jan Axelson; Lakeview Research; 306 pages; 1998; . Serial port and Microcontrollers: Principles, Circuits, and Source Codes; 1st Edition; Grzegorz Niemirowski; CreateSpace; 414 pages; 2013; . Serial Programming (Wikibook). External links FreeBSD Serial and UART Tutorial, includes standard signal definitions, history of UART ICs, and pinout for commonly used DB25 connector. UART Tutorial for Robotics, contains many practical examples. Data transmission pt:USART