Queued Serial Multi-Channel Module
MPC561/MPC563 Reference Manual, Rev. 1.2
15-50
Freescale Semiconductor
15.7.5
SCI Data Register (SCxDR)
The SCxDR consists of two data registers located at the same address. The receive data register (RDRx)
is a read-only register that contains data received by the SCI serial interface. Data is shifted into the receive
serial shifter and is transferred to RDRx. The transmit data register (TDRx) is a write-only register that
contains data to be transmitted. Data is first written to TDRx, then transferred to the transmit serial shifter,
where additional format bits are added before transmission.
12
OR
Overrun error. OR is set when a new byte is ready to be transferred from the receive serial shifter
to register RDRx, and RDRx is already full (RDRF is still set). Data transfer is inhibited until OR
is cleared. Previous data in RDRx remains valid, but additional data received during an overrun
condition (including the byte that set OR) is lost.
Note that whereas the other receiver status flags (NF, FE, and PF) reflect the status of data
already transferred to RDRx, the OR flag reflects an operational condition that resulted in a loss
of data to RDRx.
0 RDRF is cleared before new data arrives.
1 RDRF is not cleared before new data arrives.
13
NF
Noise error flag. NF is set when the receiver detects noise on a valid start bit, on any of the data
bits, or on the stop bit(s). It is not set by noise on the idle line or on invalid start bits. Each bit is
sampled three times for noise. If the three samples are not at the same logic level, the majority
value is used for the received data value, and NF is set. NF is not set until the entire frame is
received and RDRF is set.
Although no interrupt is explicitly associated with NF, an interrupt can be generated with RDRF,
and the interrupt handler can check NF.
0 No noise detected in the received data.
1 Noise detected in the received data.
For receiver queue operation NF is cleared when SCxSR is read with NF set, followed by a read
of SCRQ[0:15].
14
FE
Framing error. FE is set when the receiver detects a zero where a stop bit (one) was expected.
A framing error results when the frame boundaries in the received bit stream are not
synchronized with the receiver bit counter. FE is not set until the entire frame is received and
RDRF is set.
Although no interrupt is explicitly associated with FE, an interrupt can be generated with RDRF,
and the interrupt handler can check FE.
0 No framing error detected in the received data.
1 Framing error or break detected in the received data.
15
PF
Parity error. PF is set when the receiver detects a parity error. PF is not set until the entire frame
is received and RDRF is set.
Although no interrupt is explicitly associated with PF, an interrupt can be generated with RDRF,
and the interrupt handler can check PF.
0 No parity error detected in the received data.
1 Parity error detected in the received data.
Table 15-26. SCxSR Bit Descriptions (continued)
Bits
Name
Description
Summary of Contents for MPC561
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