MCCIRM Freescale Semiconductor / Motorola, MCCIRM Datasheet - Page 73

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

5.7.9 Receiver Status Flags and Interrupts
5.7.9.1 RDR Full Flag (RDRF)
Multichannel Communication Interface — Rev. 1.0
MOTOROLA
Six status flags are associated with the SCI receiver. RDRF is set when
a character has been received and transferred into the parallel RDR.
The OR flag is set if RDRF is already set when a new character is ready
to be transferred into the parallel RDR. The PF, NF, and FE flags alert
the user to parity, noise, and framing error conditions, respectively. The
IDLE flag is set when the MCU detects an idle line condition (a frame of
all 1s).
All status flags associated with a serially received frame are set
simultaneously. When a completed frame is received, either the RDRF
or OR flag is always set. The receiver status flags NF, FE, and PF are
set simultaneously with RDRF as appropriate. (Although error conditions
are detected as bits are received, these flags are not set until data is
transferred from the serial shifter to RDR.)
Status flags can be polled at any time by software. RDRF and IDLE can
optionally generate an automatic interrupt request. Because NF, FE,
and PF are set at the same time as RDRF, they do not have separate
interrupt enables.
To clear all receiver status flags, read the SCSR and then read the
SCDR.
RDRF is set when a character has been received and transferred into
the parallel RDR. RDRF optionally can generate an automatic interrupt
request. If RIE equals 1, an interrupt is generated whenever RDRF
changes from 0 to 1. If RIE equals 0, RDRF does not generate interrupts,
and the receiver must be polled.
Although an interrupt is not explicitly associated with NF, FE, or PF, an
interrupt can be generated with RDRF and the error flags checked in this
manner.
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SCI Submodule
Reference Manual
SCI Submodule
SCI Transmitter
73