MCCIRM Freescale Semiconductor / Motorola, MCCIRM Datasheet - Page 74

• Manufacturer Part Number: MCCIRM
• Description: MCCIRM Multi-Channel Communications Interface Reference Manual
• Manufacturer: Freescale Semiconductor / Motorola

SCI Submodule
5.7.9.2 Noise Flag (NF)
5.7.9.3 Framing Error Flag (FE)
5.7.9.4 Overrun Flag (OR)
5.7.9.5 Parity Error Flag (PF)
Reference Manual
74
NF is set when the SCI receiver detects noise on a valid start bit, on any
of the data bits, or on the stop bit. 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. Refer to
Synchronization
FE is set when the SCI receiver detects a 0 where a stop bit (one) is
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. A break
can also cause FE to be set.
Framing errors are not always detected: If a data bit in the expected stop
bit time happens to be a logic 1, the FE flag is not set.
OR is set when a new byte is ready to be transferred from the receive
serial shifter to register RDR, and RDR is already full (RDRF is still set).
In an overrun condition, the character that caused the overrun is lost, but
the previously received character in the SCDR is not disturbed. Since
framing, noise, and parity errors are detected while data is in the serial
shifter, FE, NF, and PF cannot occur simultaneously with OR.
PF is set when the SCI receiver detects a parity error. PF is not set until
the entire frame is received and RDRF is set. Although an interrupt is not
explicitly associated with PF, an interrupt may be generated with RDRF
and PF checked in this manner.
Freescale Semiconductor, Inc.
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SCI Submodule
for more information on noise detection.
Multichannel Communication Interface — Rev. 1.0
5.7.11 Frame Detection and
MOTOROLA