RM0352 datasheet(127/138 Pages) STMICROELECTRONICS

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RM0352

UART (universal asynchronous receive transmit)

137

Note:

To update the three registers there are two possible sequences:

•

UARTIBRD write, UARTFBRD write, and UARTLCR_H write

•

UARTFBRD write, UARTIBRD write, and UARTLCR_H write.

To update UARTIBRD or UARTFBRD only:

•

UARTIBRD write, or UARTFBRD write, and UARTLCR_H write.

Table 124 is a truth table for the “Stick Parity Select” (SPS), “Even Parity Select” (EPS), and

“Parity ENable” (PEN) bits of the line control register, UARTLCR_H is in

Section 12.6.7 on

page 126.

Note:

The UARTLCR_H, UARTIBRD, and UARTFBRD registers must not be changed:

•

When the UART is enabled.

•

When completing a transmission or a reception when it has been programmed to

become disabled.

The FIFO integrity is not guaranteed under the following conditions:

•

After the BRK bit has been initiated.

•

If the software disables the UART in the middle of a transmission with data in the FIFO,

and then re-enables it.

12.6.8

Control register, UARTCR

The UARTCR register is the control register. All the bits are cleared to 0 on reset except for

bits 9 and 8 that are set to 1.

Table 125 lists the register bit assignments.

Table 124. Parity truth table

PEN

EPS

SPS

Parity bit (transmitted or checked)

Not transmitted or checked

110

Even parity

Odd parity

101

111

Table 125. UARTCR register

Bits

Name

Function

CTSEn

CTS hardware flow control enable. If this bit is set to 1, CTS hardware flow control is enabled.

Data is only transmitted when the

nUARTCTS signal is asserted.

RTSEn

RTS hardware flow control enable. If this bit is set to 1, RTS hardware flow control is enabled.

Data is only requested when there is space in the receive FIFO for it to be received.

Out2

This bit is the complement of the UART Out2 (nUARTOut2) modem status output. That is, when

the bit is programmed to 1, the output is 0. For DTE this can be used as “Ring Indicator” (RI).

Out1

This bit is the complement of the UART Out1 (nUARTOut1) modem status output. That is, when

the bit is programmed to 1 the output is 0. For DTE this can be used as “Data Carrier Detect”

(DCD).

RTS

Request to send. This bit is the complement of the UART request to send,

nUARTRTS, modem

status output. That is, when the bit is programmed to 1 then

nUARTRTS is LOW.

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