MPC555
/
MPC556
QUEUED SERIAL MULTI-CHANNEL MODULE
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
14-49
14.8.5 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 se-
rial 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 trans-
mitted. Data is first written to TDRx, then transferred to the transmit serial shifter,
where additional format bits are added before transmission.
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 synchro-
nized 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.
SCxDR —
SCI Data Register
0x30 500E, 0x30 5026
MSB
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
LSB
15
RESERVED
R8/T8 R7/T7 R6/T6 R5/T5 R4/T4 R3/T3 R2/T2 R1/T1 R0/T0
RESET:
0
0
0
0
0
0
0
U
U
U
U
U
U
U
U
U
Table 14-25 SCxSR Bit Descriptions (Continued)
Bit(s)
Name
Description
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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