Queued Serial Multi-Channel Module
MPC561/MPC563 Reference Manual, Rev. 1.2
15-48
Freescale Semiconductor
15.7.4
SCI Status Register (SCxSR)
SCxSR contains flags that show SCI operating conditions. These flags are cleared either by SCIx hardware
or by a read/write sequence. The sequence consists of reading the SCxSR (either the upper byte, lower
byte, or the entire half-word) with a flag bit set, then reading (or writing, in the case of flags TDRE and
TC) the SCxDR (either the lower byte or the half-word).
The contents of the two 16-bit registers SCxSR and SCxDR appear as upper and lower half-words,
respectively, when the SCxSR is read into a 32-bit register. An upper byte access of SCxSR is meaningful
only for reads. Note that a word read can simultaneously access both registers SCxSR and SCxDR. This
action clears the receive status flag bits that were set at the time of the read, but does not clear the TDRE
or TC flags. To clear TC, the SCxSR read must be followed by a write to register SCxDR (either the lower
byte or the half-word). The TDRE flag in the status register is read-only.
If an internal SCI signal for setting a status bit comes after the CPU has read the asserted status bits but
before the CPU has read or written the SCxDR, the newly set status bit is not cleared. Instead, SCxSR must
be read again with the bit set and SCxDR must be read or written before the status bit is cleared.
NOTE
None of the status bits are cleared by reading a status bit while it is set and
then writing zero to that same bit. Instead, the procedure outlined above
must be followed. Note further that reading either byte of SCxSR causes all
16 bits to be accessed, and any status bits already set in either byte are armed
to clear on a subsequent read or write of SCxDR.
10
RIE
Receiver interrupt enable
0 SCI RDRF and OR interrupts disabled.
1 SCI RDRF and OR interrupts enabled.
11
ILIE
Idle-line interrupt enable
0 SCI IDLE interrupts disabled.
1 SCI IDLE interrupts enabled.
12
TE
Transmitter enable
0 SCI transmitter disabled (TXD pin can be used as general-purpose output)
1 SCI transmitter enabled (TXD pin dedicated to SCI transmitter).
13
RE
Receiver Enable
0 SCI receiver disabled (RXD pin can be used as general-purpose input).
1 SCI receiver enabled (RXD pin is dedicated to SCI receiver).
14
RWU
Receiver wakeup. Refer to
Section 15.7.7.10, “Receiver Wake-Up
.”
0 Normal receiver operation (received data recognized).
1 Wakeup mode enabled (received data ignored until receiver is awakened).
15
SBK
Send break
0 Normal operation.
1 Break frame(s) transmitted after completion of current frame.
Table 15-25. SCCxR1 Bit Descriptions (continued)
Bits
Name
Description
Summary of Contents for MPC561
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