Datasheet

DocID024647 Rev 1 127/138
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)
0 x x Not transmitted or checked
110 Even parity
1 0 0 Odd parity
101 1
111 0
Table 125. UARTCR register
Bits Name Function
15 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.
14 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.
13 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).
12 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).
11 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.