K60P100M100SF2RM Datasheet, PDF (1495/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Field
4
IDLE
3
OR
2
NF
1
FE
Chapter 51 Universal Asynchronous Receiver/Transmitter (UART)
UARTx_S1 field descriptions (continued)
Description
0 The number of datawords in the receive buffer is less than the number indicated by RXWATER.
1 The number of datawords in the receive buffer is equal to or greater than the number indicated by
RXWATER at some point in time since this flag was last cleared.
Idle Line Flag
IDLE is set when 10 consecutive logic 1s (if C1[M] = 0), 11 consecutive logic 1s (if C1[M] = 1 and C4[M10]
= 0), or 12 consecutive logic 1s (if C1[M] = 1, C4[M10] = 1, and C1[PE] = 1) appear on the receiver input.
After 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) or a LIN break character must set the S2[LBKDIF] flag before an
idle condition can set the IDLE flag. To clear IDLE, read UART status S1 with IDLE set and then read D.
Idle detection is not supported when 7816E is set/enabled and hence this flag is ignored.
NOTE: When the receiver wakeup bit (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 get 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.
Receiver Overrun Flag
OR is set when software fails to prevent the receive data register from overflowing with data. The OR bit
is set immediately after the stop bit has been completely received for the dataword that overflows the
buffer and all the other error flags (FE,NF and PF) are prevented from setting. The data in the shift
register is lost, but the data already in the UART data registers is not affected. If the OR flag is set, no
data will be stored in the data buffer even if sufficient room exists. Additionally, while the OR flag is set the
RDRF flag, and IDLE flags will be blocked from asserting, i.e. transition from an inactive to an active state.
To clear OR, read S1 when OR is set and then read UART data register (D). If LBKDE is enabled and a
LIN Break is detected, the OR bit will assert if the S2[LBKDIF] flag is not cleared before the next data
character is received.See Overrun (OR) flag implications for more details regarding the operation of the
OR bit. In 7816 mode, it is possible to configure a NACK to be returned by programing the
C7816[ONACK] bit.
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.
Noise Flag
NF is set when the UART detects noise on the receiver input. NF bit does not get set in the case of an
overrun or while the LIN break detect feature is enabled (S2[LBKDE] = 1). When NF is set, it only
indicates that a dataword has been received with noise since the last time it was cleared. There is no
guarantee that the first dataword read from the receive buffer has noise or that there is only one dataword
in the buffer that was received with noise unless the receive buffer has a depth of one. To clear NF, read
S1 and then read the UART data register (D).
0 No noise detected since the last time this flag was cleared. If the receive buffer has a depth greater
than 1 then there may be data in the receiver buffer that was received with noise.
1 At least one dataword was received with noise detected since the last time the flag was cleared.
Framing Error Flag
FE is set when a logic 0 is accepted as the stop bit. FE bit does not set in the case of an overrun or while
the LIN break detect feature is enabled (S2[LBKDE] = 1). FE inhibits further data reception until it is
cleared. To clear FE, read S1 with FE set and then read the UART data register (D). The last data in the
receive buffer represents the data that was received with the frame error enabled. However, framing
errors are not supported when 7816E is set/enabled. However, if this flag is set, data will still not be
received in 7816 mode.
Table continues on the next page...
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
1495