M16C User Manual.pdf

UARTMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER2.5 Clock-Asynchronous Serial I/O (UART)2.5.1 OverviewUART handles communications by means of character-by-character synchronization. The transmissionside and the reception side are independent of each other, so full-duplex communication is possible. Thefollowing is an overview of the clock-asynchronous serial I/O.(1) Transmission/reception formatFigure 2.5.1 shows the transmission/reception format, and Table 2.5.1 shows the names and functionsof transmission data.Transfer data length : 7 bits 1ST – 7DATA 1SP1ST – 7DATA 2SP1ST – 7DATA – 1PAR – 1SP1ST – 7DATA – 1PAR – 2SPTransfer data length : 8 bits 1ST – 8DATA 1SP1ST – 8DATA 2SP1ST – 8DATA – 1PAR – 1SP1ST – 8DATA – 1PAR – 2SPTransfer data length : 9 bits 1ST – 9DATA 1SP1ST – 9DATA 2SP1ST – 9DATA – 1PAR – 1SP1ST – 9DATA – 1PAR – 2SPST : Start bitDATA : Character bit (Transfer data)PAR : Parity bitSP : Stop bitFigure 2.5.1. Transmission/reception formatTable 2.5.1. Transmission data names and functionsNameST (start bit)FunctionA 1-bit “L” signal to be added immediately before character bits.This bit signals the start of data transmission.DATA (character bits)PAR (parity bit)SP (stop bit)Transmission data set in the UARTi transmit buffer register.A signal to be added immediately after character bits so as to increase datareliability. The level of this signal so varies that the total number of 1's incharacter bits and this bit always becomes even or odd depending on whichparity is chosen, even or odd.Either 1-bit or 2-bit “H” signal to be added immediately after character bits (afterthe parity bit if parity is checked). This / they signals the end of datatransmission.348