UARTx_S1 field descriptions (continued)Field Description0 Receive data buffer is empty.1 Receive data buffer is full.4IDLEIdle Line FlagAfter the IDLE flag is cleared, a frame must be received (although not necessarily stored in the data buffer,for example if C2[RWU] is set). To clear IDLE, read UART status S1 with IDLE set and then read D.IDLE is set when either of the following appear on the receiver input:• 10 consecutive logic 1s if C1[M] = 0• 11 consecutive logic 1s if C1[M] = 1 and C4[M10] = 0• 12 consecutive logic 1s if C1[M] = 1, C4[M10] = 1, and C1[PE] = 1Idle detection is not supported when7816Eis set/enabled and hence this flag is ignored.NOTE: When RWU is set and WAKE is cleared, an idle line condition sets the IDLE flag if RWUID is set,else the IDLE flag does not become set.0 Receiver input is either active now or has never become active since the IDLE flag was last cleared.1 Receiver input has become idle or the flag has not been cleared since it last asserted.3ORReceiver Overrun FlagOR is set when software fails to prevent the receive data register from overflowing with data. The OR bit isset immediately after the stop bit has been completely received for the dataword that overflows the bufferand all the other error flags (FE, NF, and PF) are prevented from setting. The data in the shift register islost, but the data already in the UART data registers is not affected. If the OR flag is set, no data is storedin the data buffer even if sufficient room exists. Additionally, while the OR flag is set, the RDRF and IDLEflags are blocked from asserting, that is, transition from an inactive to an active state. To clear OR, readS1 when OR is set and then read D. See functional description for more details regarding the operation ofthe OR bit. In 7816 mode, it is possible to configure a NACK to be returned by programingC7816[ONACK].0 No overrun has occurred since the last time the flag was cleared.1 Overrun has occurred or the overrun flag has not been cleared since the last overrun occured.2NFNoise FlagNF is set when the UART detects noise on the receiver input. NF does not become set in the case of anoverrun. To clear NF, read S1 and then read D.0 No noise detected.1 Noise detected in the received character in D.1FEFraming Error FlagFE is set when a logic 0 is accepted as the stop bit. FE does not set in the case of an overrun. FE inhibitsfurther data reception until it is cleared. To clear FE, read S1 with FE set and then read D. The last data inthe receive buffer represents the data that was received with the frame error enabled. Framing errors arenot supported when 7816E is set/enabled. However, if this flag is set, data is still not received in 7816mode.0 No framing error detected.1 Framing error.0PFParity Error FlagPF is set when PE is set and the parity of the received data does not match its parity bit. The PF is not setin the case of an overrun condition. To clear PF, read S1 and then read D.Table continues on the next page...Memory map and registersKL27 Sub-Family Reference Manual , Rev. 5, 01/2016688 Freescale Semiconductor, Inc.
