UARTx_C2 field descriptions (continued)Field DescriptionThis bit can be written to 1 to place the UART receiver in a standby state where it waits for automatichardware detection of a selected wakeup condition. The wakeup condition is an idle line betweenmessages, WAKE = 0, idle-line wakeup, or a logic 1 in the most significant data bit in a character, WAKE =1, address-mark wakeup. Application software sets RWU and, normally, a selected hardware conditionautomatically clears RWU.0 Normal UART receiver operation.1 UART receiver in standby waiting for wakeup condition.0SBKSend BreakWriting a 1 and then a 0 to SBK queues a break character in the transmit data stream. Additional breakcharacters of 10 to 13, or 13 to 16 if BRK13 = 1, bit times of logic 0 are queued as long as SBK is set.Depending on the timing of the set and clear of SBK relative to the information currently being transmitted,a second break character may be queued before software clears SBK.0 Normal transmitter operation.1 Queue break character(s) to be sent.36.2.5 UART Status Register 1 (UARTx_S1)Address: 4006_A000h base + 4h offset = 4006_A004hBit 7 6 5 4 3 2 1 0Read TDRE TC RDRF IDLE OR NF FE PFWrite w1c w1c w1c w1c w1cReset 1 1 0 0 0 0 0 0UARTx_S1 field descriptionsField Description7TDRETransmit Data Register Empty FlagTDRE is set out of reset and whenever there is room to write data to the transmit data buffer. To clearTDRE, write to the UART data register ( UART _D).0 Transmit data buffer full.1 Transmit data buffer empty.6TCTransmission Complete FlagTC is set out of reset and when TDRE is set and no data, preamble, or break character is beingtransmitted.TC is cleared automatically by one of the following:• Write to the UART data register ( UART _D) to transmit new data• Queue a preamble by changing TE from 0 to 1• Queue a break character by writing 1 to UART _C2[SBK]0 Transmitter active (sending data, a preamble, or a break).1 Transmitter idle (transmission activity complete).Table continues on the next page...Chapter 36 Universal Asynchronous Receiver/Transmitter (UART0)KL04 Sub-Family Reference Manual, Rev. 3.1, November 2012Freescale Semiconductor, Inc. 627
