80C186EC/80C188EC Microprocessor User's Manual

SERIAL COMMUNICATIONS UNIT
Register Name:
Register Mnemonic:
Register Function:
Serial Status Register
SxSTS
Indicates the status of the serial port.
15 0
D
B
R
K
1
D
B
R
K
0
R
B
8/
P
E
R
I
T
I
F
E
T
X
E
O
E
C
T
S
A1278-0A
Bit
Mnemonic
Bit Name
Reset
State
Function
FE Framing Error 0 FE is set when a framing error occurs. A
framing error occurs when a valid stop bit is not
detected.
TXE
Transmitter
Empty
1 TXE is set when both SxTBUF and the transmit
shift register are empty. TXE determines when
two consecutive bytes can be written to
SxTBUF for transmission. Accessing SxSTS
does not clear TXE.
OE Overrun Error 0 OE is set when an overrun error occurs. An
overrun error occurs when the character in
SxRBUF is not read before another complete
character is received. SxRBUF always contains
the most recent reception.
CTS Clear To Send 0 CTS is the complement of the value on the CTF
pin. Accessing SxSTS does not clear CTS.
NOTE:
Reserved register bits are shown with gray shading. Reserved bits must be written
to a logic zero to ensure compatibility with future Intel products.
Figure 11-14. Serial Port Status Register (Continued)
When either BREAK character is detected, an overrun error occurs (OE is set). SxRBUF will contain
at least one null character.
11-17