
Serial Communications Interface (SCI)
SCI Registers
MC68HC11E Family
—
Rev. 4
Technical Data
MOTOROLA
Serial Communications Interface (SCI)
155
RWU
—
Receiver Wakeup Control Bit
0 = Normal SCI receiver
1 = Wakeup enabled and receiver interrupts inhibited
SBK
—
Send Break
At least one character time of break is queued and sent each time
SBK is written to 1. As long as the SBK bit is set, break characters are
queued and sent. More than one break may be sent if the transmitter
is idle at the time the SBK bit is toggled on and off, as the baud rate
clock edge could occur between writing the 1 and writing the 0 to SBK.
0 = Break generator off
1 = Break codes generated
7.8.4 Serial Communication Status Register
The SCSR provides inputs to the interrupt logic circuits for generation of
the SCI system interrupt.
TDRE
—
Transmit Data Register Empty Flag
This flag is set when SCDR is empty. Clear the TDRE flag by reading
SCSR with TDRE set and then writing to SCDR.
0 = SCDR busy
0 = SCDR empty
Address:
$102E
Bit 7
6
5
4
3
2
1
Bit 0
Read:
TDRE
TC
RDRF
IDLE
OR
NF
FE
Write:
Reset:
1
1
0
0
0
0
0
0
= Unimplemented
Figure 7-6. Serial Communications Status Register (SCSR)