UART based autobauding without data loss

摘要

The cellular telephone includes a universal asynchronous receive and transmit (UART) chip for receiving data in a serial format from an external source, such as a laptop computer, and for converting the serial data to parallel bytes of data for transmission to a microcontroller of the cellular telephone. The UART operates in one of two modes: a sample mode and a byte mode. In the sample mode, voltage levels of serial data signals received by the UART are detected and sample bytes are generated representative of those voltage levels. The sample bytes are stored within a receive First In First Out (FIFO) queue of the UART for eventual transference to the microcontroller. The microcontroller converts the sample bytes to signals appropriate for transmission using a cellular transmission format such as code division multiple access (CDMA). In the byte mode, the UART receives data bytes as bytes and stores those bytes directly within the receive FIFO without any sampling. The data bytes stored within the receive FIFO are transferred to the microcontroller which converts the bytes to appropriate signals for transmission from the cellular telephone. By processing input data as bytes rather than as samples, the microcontroller consumes far fewer resources processing the data thereby achieving, among other advantages, overall power reduction. In use, the UART is controlled to initially receive data as samples. The microcontroller examines the samples to determine the baud rate of received data then controls the UART to switch to the byte processing mode using the detected baud rate. Techniques for determining the baud rate and for switching the UART to byte mode without loss of data are also described herein.