Serial Communications Interface (S08SCIV1)
MC9S08RC/RD/RE/RG Data Sheet, Rev. 1.11
Freescale Semiconductor
155
12.2.5
SCI Status Register 2 (SCI1S2)
This register has one read-only status ag. Writes have no effect.
12.2.6
SCI Control Register 3 (SCI1C3)
76543210
R
0000000
W
Reset
00000000
= Unimplemented or Reserved
Figure 12-8. SCI Status Register 2 (SCI1S2)
Table 12-6. SCI1S2 Register Field Descriptions
Field
Description
0
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 ag can be used to check whether an
SCI character is being received before instructing the MCU to go to stop mode.
0 SCI receiver idle waiting for a start bit.
1 SCI receiver active (RxD input not idle).
76543210
R
0
W
Reset
00000000
= Unimplemented or Reserved
Figure 12-9. SCI Control Register 3 (SCI1C3)
Table 12-7. SCI1C3 Register Field Descriptions
Field
Description
7
R8
Ninth Data Bit for Receiver — When the SCI is congured 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 SCI1D register. When reading 9-bit data,
read R8 before reading SCI1D because reading SCI1D completes automatic ag clearing sequences which
could allow R8 and SCI1D to be overwritten with new data.
6
T8
Ninth Data Bit for Transmitter — When the SCI is congured 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 SCI1D register. When writing 9-bit data, the entire
9-bit value is transferred to the SCI shift register after SCI1D is written so T8 should be written (if it needs to
change from its previous value) before SCI1D 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 SCI1D is written.
5
TXDIR
TxD Pin Direction in Single-Wire Mode — When the SCI is congured for single-wire half-duplex operation
(LOOPS = RSRC = 1), this bit determines the direction of data at the TxD pin.
0 TxD pin is an input in single-wire mode.
1 TxD pin is an output in single-wire mode.