MCU Serial Communications Interface (SCI)
MC1321x Reference Manual, Rev. 1.6
Freescale Semiconductor
18-15
18.9.5
SCI1
Status Register 2 (SCIxS2)
This register has one read-only status flag. Writes have no effect.
Figure 18-9. SCI1
Status Register 2 (SCIxS2)
RAF — Receiver Active Flag
RAF is set when the SCI receiver detects the beginning of a valid start bit, and RAF is cleared
automatically when the receiver detects an idle line. This status flag can be used to check whether an
SCI character is being received before instructing the MCU to go to Stop Mode.
1 = SCI receiver active (RxD1 input not idle).
0 = SCI receiver idle waiting for a start bit.
18.9.6
SCI1
Control Register 3 (SCIxC3)
Figure 18-10. SCI1
Control Register 3 (SCIxC3)
R8 — Ninth Data Bit for Receiver
When the SCI is configured for 9-bit data (M = 1), R8 can be thought of as a ninth receive data bit to
the left of the MSB of the buffered data in the SCIxD register. When reading 9-bit data, both R8 and
SCIxD must be read to complete the automatic RDRF clearing sequence.
T8 — Ninth Data Bit for Transmitter
When the SCI is configured for 9-bit data (M = 1), T8 may be thought of as a ninth transmit data bit to
the left of the MSB of the data in the SCIxD register. When writing 9-bit data, the entire 9-bit value is
transferred to the SCI shift register after SCIxD is written so T8 should be written (if it needs to change
from its previous value) before SCIxD is written. If T8 does not need to change in the new value (such
as when it is used to generate mark or space parity), it need not be written each time SCIxD is written.
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
0
0
0
0
Write:
Reset:
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
Write:
Reset:
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
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