Serial Communications Interface (SCI)
SCI Registers
M68HC11E Family — Rev. 5
Data Sheet
MOTOROLA
Serial Communications Interface (SCI)
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125
7.7.4 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
TC — Transmit Complete Flag
This flag is set when the transmitter is idle (no data, preamble, or break
transmission in progress). Clear the TC flag by reading SCSR with TC set and
then writing to SCDR.
0 = Transmitter busy
1 = Transmitter idle
RDRF — Receive Data Register Full Flag
This flag is set if a received character is ready to be read from SCDR. Clear the
RDRF flag by reading SCSR with RDRF set and then reading SCDR.
0 = SCDR empty
1 = SCDR full
IDLE — Idle Line Detected Flag
This flag is set if the RxD line is idle. Once cleared, IDLE is not set again until
the RxD line has been active and becomes idle again. The IDLE flag is inhibited
when RWU = 1. Clear IDLE by reading SCSR with IDLE set and then reading
SCDR.
0 = RxD line active
1 = RxD line idle
OR — Overrun Error Flag
OR is set if a new character is received before a previously received character
is read from SCDR. Clear the OR flag by reading SCSR with OR set and then
reading SCDR.
0 = No overrun
1 = Overrun detected
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)
F
Freescale Semiconductor, Inc.
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