COP684EG datasheet(22/48 Pages) NSC

22 / 48 page

UART

The device contains a full-duplex software programmable

UART The UART

(Figure 11) consists of a transmit shift

isters as follows a transmit buffer register (TBUF) a receiv-

er buffer register (RBUF) a UART control and status regis-

ter (ENU) a UART receive control and status register

(ENUR) a UART interrupt and clock source register (ENUI)

a prescaler select register (PSR) and baud (BAUD) register

The ENU register contains flags for transmit and receive

functions this register also determines the length of the

data frame (7 8 or 9 bits) the value of the ninth bit in trans-

mission and parity selection bits The ENUR register flags

framming data overrun and parity errors while the UART is

receiving

Other functions of the ENUR register include saving the

ninth bit received in the data frame enabling or disabling the

UART’s attention mode of operation and providing addition-

al receivertransmitter status information via RCVG and

XMTG bits The determination of an internal or external

clock source is done by the ENUI register as well as select-

ing the number of stop bits and enabling or disabling trans-

mit and receive interrupts A control flag in this register can

also select the UART mode of operation asynchronous or

synchronous

TLDD11214 – 23

FIGURE 11 UART Block Diagram

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COP684EG Datasheet(PDF) 22 Page - National Semiconductor (TI)